Tbol is my favorite oral and very good at what it does with minimal sides (other than heartburn). Unless you are 100lbs, 20mg isn't going to do anything noticeable in a test environment. I'd do atleast 40mg. I think there are better ways to harden up and drop water than tbol (masteron/proviron/AI), but if you are looking to kick into a higher gear and gain a couple more pounds at the end, then it's good - I've never found tbol to have that really pronounced androgen hardening effect - it just don't aromatise so itself makes you look hard outside the presence of inflated estrogen. I don't know how hard it will make you in the presence of inflated estrogen from exogenous test - it won't add water, but there are better additions to harden you up.