I would limit (but not recommend at all) to subcutaneous only for test on TRT.
But the last thing I would inject on subcutaneous is very high potent and concentrated product like Big N Full, you take lot of risk to develop complication like infections, abscess,…
Big N full can create easily inflammation reaction (on IM) because it is dosed at 600mg per ml, that’s why it has to be injected properly to have a correct diffusion in the muscle, so under the skin will be a terrible idea as it will have a very bad diffusion