For your initial question, I feel like GLPs are definitely the easier to fully dissolve peptides out there. I used to do 10 mg/ml, but when I saw the light and learned from some kind community members right here in this forum, I now go with 20 mg/ml. Works for tirz, and I am mostly certain it works for Reta. Trying this in 2 weeks when I recon my next vials/filter. (I have T30s and R20s, I recon 2x T30s, filtered in a sterile vial to make a T60 (plus whatever overfill), I only do 1 R20 now, but moving to 2x to make R40 in 2 weeks). So yeah, concentrate them how you like! 10 mg/ml is easiest for dosage mental math, but honestly, 5 or 20 isn’t too heavy of a mental lift.
Not sure if you were looking for demographic info here, but my wife and I are both early 40s. Both take tirz (She takes 6, I take 9), on Fridays.
I take 4 mg Reta on Mondays in addition to Friday tirz. I understand that Reta is a bit better for body recomp if you’re working out, but maybe less great at handling food noises. I’ve started working out more with better weather out there, and to “tide me over” with Tirz half life being 5 days. Plan on bumping up to 6 tomorrow, or maybe trying to hold out for one more week. Wife may also join me, starting with 2 mg/week on Monday.
Of course, dosages and reasoning is anecdotal and based on compiled reading over the months, so certainly don’t take my word as “the way”. It has been working for me, 6 months in, 48 lbs gone, and according to my smart scale which isn’t super accurate, decreased body fat from 38.8% to 30.1%, visceral fat 20 to 14, lean muscle from 156.5 lbs to 147 lbs. (just hit a milestone so really excited to post these numbers, they may not matter to most. Just me)