I hope other people chime in here with their opinions as well, particularly real RPR owners, which I am not. But effectively, I would treat the RPR like an AR-15 for ergonomic purposes. You have a Picatinny rail that's about the same height as it is on an AR, and it's a monolithic rail that's extending forward well beyond the objective lens of your optic, so there's no "drop" past the rail to the barrel. Also, you have a straight line stock, like an AR, with an extendable cheek piece that raises up but not down. So, you can get penalized for having rings that are too short with a cheek weld problem in the rear or the objective of the scope hitting the rail in the front, but the only penalty for rings that are too tall is more height over bore.
I would treat it like an AR and go with AR-height or extra tall rings. Doing a couple of quick Google image searches I'm also seeing a lot of guys running one piece QD mounts intended for ARs, which I think verifies that we are in the right ballpark if we treat the RPR like an AR-15 for mounting purposes.