I have done tren a sub-q. It left me with a knot on my abdomen for three weeks. Did 1ml and I didn't skip a beat with my gains. I used to sub-q TNE all the time last year. Instead of taking just a minute or two to get that funky taste in your mouth, it took about 5-8 minutes after inject. Absorption is definitely a little slower but I wouldn't say by much.
