I've been doing SC injections in a 4" radius around my belly button with a 1/2" insulin needle (30 gauge) Mon/Wed/Fri since June, and have noticed no negative effects whatsoever.
I'm still dosing the same total amount (200 mg test cyp per week) that I was Jan-May, but SC is way less of a pain -- literally -- than IM, and it's far easier to inject in the stomach than it is to reach around and try and inject in the glutes while remaining relaxed. The 30 gauge needle requires only marginally more force to depress the plunger than a 26 gauge needle, and the 1/2" vs. 1" needle makes a gigantic difference: i.e., no pain at all. If you backload the insulin needle, the tip slides right into your stomach like a hot knife through butter.
As far as test results, my first labs (8 weeks out) had TT of roughly 650, FT 38, and my recent labs (10 months after starting TRT) have TT over 1200 and FT over 50 [per MD over the phone; I'll post labs after I see him next week]. So SC is clearly not cratering my test levels.