I've tried experimenting with 5-htp many times, and found that it benefits me more taking it after rolling. I take about 100 mg when I come down and another 100 mg each day for 2 to 3 days afterward. Maybe bump it up to 150mg or so if you've dosed more heavily. It doesn't eliminate the comedown and aftereffects, but it does help improve your mood and appetite while the MDMA wears off. As for taking it before, it does seem to weaken the roll, especially when taken a short time before dropping. I'm not sure about taking a 24 hr or more break between preloading and dropping. Never really experimented with that aspect. I was more concerned with making my comedowns less harsh, and figured taking long enough breaks and being smart about my health were the best ways to ensure a memorable roll before dropping.
So yeah, concentrate more on establishing your own regimen for afterward (i'm of a similar build to you btw), and if you really want to, try and see if a preload regimen works for you. everybody's different.