Mixing your peptides is a big topic and one i have researched alot.
In my opinion Blends would not have been made if they dont work.
Also some peptides work synergistic together so i feel that they can be mixed in the same syringe.
I have done all of the above, and realized that for me its faster to have my peptides in each individual pen and control the dose.
But yeah i do understand that some just want reduce how many injections they do but its sorta of a hassle to mix them all up, so for me its faster to just pin separately.
Now i do have a process for GHK-CU and that one I draw to a syringe, and then fill with bac then swap the needle and shoot.
I also sometimes mix bpc, ghk-cu and the remainder in bac and the bpc helps with the burn.