"In case it isn't clear, these letters are of the "happy to help you with your awesome project" variety, and not of the "I would like to tell the panel that this person is awesome" type of talk that is similar to the recommendation letter." --DM
Letters along the line of "this person is awesome" are ignored. Letters of support from a collaborator along the lines of "Dear Person X: I am so glad to participate in your project and do QRP for you" are not only critical but necessary. --Potnia
Here is what I wrote about this a while ago.
Here is a letter that some(marvelous)one wrote for me, about a project for which I require his support (he can do stuff I can't do). In this example, I've done bunny hopping, but not in infant bunnies. He is a Big Dog, working on infant bunnies, but not hopping. I've added interpretation between the lines:
The letter is from my colleague to me. Not to the NIH. This suggests and supports the idea that we have a working relationship.
This letter is to document my willingness and in fact eagerness to collaborate with you on your proposal titled "The Effect of prenatal nutritional supplements on bunny hopping in neonatal rabbits”.
First, bluntly state the purpose of the letter. Do not waste words on euphemisms or betting around the bush. Prof. Big Dog is supporting, nay he is eager, to help me. Also, get the title of the proposal right. Getting it wrong could imply that we’re not quite so close as I would like the committee to believe.
The concepts and hypotheses you have developed are very timely because of the increasing number bunnies born that have trouble hopping and are surviving birth only to meet untimely death in the jaws of vicious foxes.
This is a statement of what the proposal is about. Again, this shows that we’ve actually talked about things. Given that Prof Big Dog is over extended and doing too much, it’s important that the study section perceive that he (Prof. Big Dog) knows what he is supporting and that it’s not just a reflexive, rote letter.
As you know, I have been using pregnant and newborn rabbits for almost 20 years and 7 of those here at Massive Agricultural and Ecological University as a model to study the consequences of preterm nutrition and to understand and improve the protocols for baby bunnies.
This is a statement about what Prof. Big Dog does, and how long he’s been doing it, and that he knows something about the field (for those unaware of his reputation as a Big Dog).
We know from our numerous studies of such bunnies often have problems with hopping, although we have not addressed that issue. By focusing on the issues of hopping, you addressing a critical issue and hole in our understanding of the survival of infant bunnies.
Prof Big Dog is tying our two programs together. What he does and what’s missing, which is what I am proposing to do.
My program works with 100 pregnant rabbits each year which has provided us with valuable experience and insights into the harvest and post-delivery care of baby bunnies. By this letter I confirm my willingness to participate in your study and provide you with assistance in performing the various things necessary to get the infants you need to study hopping. This will include providing you with our protocols and training members of your research team.
Specifics on what Prof. Big Dog does. It also contains explicit statements of what he will do for me. Make sure this matches up with the text in the proposal. If it is critical to the success of the project, make sure you mention Prof. Big Dog in the places where those particular skills/methods/interpretations are important.
From a selfish perspective, I am eager to learn more about the development of hopping. It is important to emphasize how the relevance the bunny model to understanding infant human disease, and that our results have made it possible for us to translate our findings into my practice as a pediatrician.
Prof. Big Dog uses the magic word du jour of “translation” (which, mind you, may not always be the magic word. “optogenetics” or “CRISPR” is also good here, if appropriate). It also emphasizes that Prof. Big Dog understands what is important about doing this work, from the perspective of meeting the NIH mission.
I am confident it will be possible to apply your findings about hopping to the larger concerns about baby bunnies. I look forward to welcoming you to the group of labs that use bunnies as a relevant and translational model for human infants. I wish you success with this exciting and much needed research.
More nice things from Prof. Big Dog, reiterating the important points for NIH, his confidence in the importance of my proposal, but also that I am joining a community of people doing something NIH wants done.
NOW: the money point. I didn't write a draft for Prof. Big Dog. He did this, and he knows what he is doing. BUT! This is not always true. It is always acceptable/fair to write something like this to a person who has offered to help and support your proposal:
Dear Prof Big Dog,
Thank you for your willingness to support my proposal, and for writing a letter of support, on the development of hopping in baby bunnies. Your expertise on baby bunnies will be critical to the success of my project. I am happy to provide you with bullet points for this letter, or even draft some text if that would be useful to you. The proposal is due in my grants office on Sept 20, so if you could get me the letter by Sept 17 or 18 that would be great. I look forward to a collaboration that will improve the field of baby bunny care. Sincerely, Potnia