I'm a western pleasure rider and not cutting the mane is a big no no in my arena. My horses manes are under 2 inches and are banded with about 30-40 bands.
BUT, that's not everyones cup of tea. If a judge is a real judge they should not glance at a horse and go "hm... that mane is not approx. 1 inch and 3/4 inch. THEY'RE ELIMINATED!"
I suggest what you do is you brush,brush,brush. Trim the ends just to give it a nice look even if its long. Depending on the length maybe band? But that's totally up to you.
You can always use gel so it stays nice and smooth and all down.
Just so long as he doesnt go in there with bed head I'm sure it'll be fine =)
Hope that's helpful!
Tino's Nugget - 16.2hh Palomino Quarterhorse / Zip And Scotch - 15.2hh Palomino Quarterhorse
She's In A Tizzy - 16.3hh Dark Bay Thoroughbred / Dreaming Of Geneva -Grey 15.3hh Thoroughbred