As others have said most pers write it in memo format but DMCA 3 doesn't really care that much, they much rather get something from the member. It is up to you what you want to put in the representation. Anecdotally the ones I have processed were a mixed bag with most being simple 1-2 pagers asking for a period of retention, while others were tens to hundreds of pages. The longer ones were generally because the mbr they did not warrant a AR/MEL and were usually using other doctors reports or adding in other documentation missed or they felt was relevant.
Don't worry about the time limit too much though. They may have tweaked their operating procedures but in the past they don't even re-visit the file for 6 months after they they send the disclosure even if they received the representation already (to treat all files the same) and they will generally ping the unit 30 days before the end of that time period if they haven't heard anything. They want to ensure that the member is afforded procedural fairness and will move dates around/if that doesn't happen to the benefit of the mbr.
