Well personally...... Im fortunate in that PIP from many things do not bother me as much, depending on the location. I will suggest staying out of ANY small muscle group, biceps, triceps, and staying in the larger muscle groups such as glutes, delts. Some pin quads with no issues, and I used to be big on pinning quads but the older I get, the more I stay out of my quads with pinning, and stick to VG, delts, glutes.....
Suspension is a great preworkout tool, but like you said..... Frequent pinning of test suspension PIP definitely comes into play and rather quickly. I personally use it on my heaviest workout days, or when I feel Im simply lagging, or focusing on bringing up a lagging bodypart. So lets say Im really focusing on lats and delts, Ill pin the suspension on those days, just to get the added aggression and push I need in the gym. Now, from a "cycling" stand point, some may be against it, but in reality, it works well for me and I do what I want with my body so Its fine by me.
Also, I have found overall volume in administering shots as well, and the depth helps also, this is PERSONAL opinion. So for me, Ill take 1/2cc of suspension in each delt rather than pinning all 1cc, so almost bi laterally splitting up the pin and this seems to help me personally. So burying the pin for me helps get the compound deepest into the muscle, once again, personal opinion but has worked well for me, plus splitting up the pins also help as well simply because there is only half the amount going into each shot.