I had the Union forces ready to go on my Elan/Artec board just this week. The L/XL size should work fine for you, but I ended up going with the Artec bindings that matched up on my stick. (Not because the Unions aren't great). However, we noticed the base didn't slide out quite as far as we would of liked, but it looked like it was going to be fine. The Unions are sweet.
Yea the Legacy is the right in between board, which lends to the style of riding I enjoy as well. Firm enough for free riding, but enough flex and pop to hit the park as well. It's a good call for sure.