Only thing to be careful of is Sub-q seems to metabolize differently (significantly in males at least). The same dose used for IM may not give the same resulte Sub-q. I have seen where guys can run much lower doses sub-q than what it takes IM to reach certain blood levels. (that may be a good thing for a female).
Also estrogen conversion seemed to be higher. I have zero idea how this would impact a female, but saying if you are going to experiment with this route, it might be a good idea to get bloodwork at about 6-7 weeks. See where test and E are at.
I use 29g 1/2" for all my IM injections, but I am fairly lean. That would probably not be the best idea for a female who tend to have thicker skinfolds (even at lower bf levels). You want an IM depot far enough in the muscle tissue.
If you want to do IM, They do make 27g luer lock needles and even 29 I believe, which if you are using a 1ml syringe will inject oils without a ton of effort. A 3ml has so much more surface area it takes about 4-5 times the force (just a guess but simple hydraulics).