Since you can't use winny... and are looking at Halo, you will want to know what the risk is using a very harsh oral like Halo vs. Proviron or another oral. Choose wisely bro. Also, Mast is pretty good but I noticed the best results and hardening when my BF% was around 10% and even lower. Also, keep in mind the dose a monsta like you might need and cost ,not too much of a hinderance for you I know but a suggestion is all. With your low BF and size I would start with least harsh compound first bro...then maybe Halo. I just ordered some HG Halo so I can give you a better more accurate answer after that but again, I tried all the other compounds first.
If I were you I would go: Test, proviron, var, mast.
(noted: tren is not an option for you either)