Groove breifs are great for single ply federations, just a mental thing, in my opinion. Go at least two sizes above what inzer recommends because they don't know shit from apple butter about sizing. It's basically another item they can sell to single ply lifters thats allowed in most federations.
From what i have heard, if you compete in a federation that allows no holds barred equipment, us poly breifs with a canvas suit or denim breifs with a poly suit, although it's too friggin expensive and too friggin timely to figure out for yourself.
On a side note, i have heard from a good IPA competitor that has used a lot of stuff, Metal breifs have no pop in the hole, Frantz are much better and less expensive. Also Ginny Phillips makes the best fucking custom canvas suit out there.
Hope things go well, let me know if you need any more useless info!!!