@deewayne2003 Thanks for the info, I'll keep looking around at what's available and have a bit of a think about it. I've been in touch with the Chapuis product manager here and he has advised that Chapuis make a small weaver style rail for the doubles, so I have got one of those on order, should arrive in around a month or so. Also he was recommending a full size red dot, the Aimpoint Micro H-2 over an RMR. I think mostly because a red dot like this is more designed for hunting rifles which makes sense but they are significantly bigger/bulkier than an RMR which is obviously a down side.
@Aussie_Hunter Congrats on a beauty of a rifle. Did you ever get your weaver rail? I have a 450-400 and I bought the weaver rail recently and I have absolutely no idea how it would work. It's longer than both slots that are in the rib and it is the short rail #66010 that's in their brochure. Looks just like the picture of it.
At first I thought that relief cut in the back was to slide over the rib for some odd reason, but that just seemed like an absurd way to go about things and the thickness of the mount and rib didn't make that even possible if you were to remove that base plate, which so far I can't because I can't get the screws to come loose. If anyone has any insight on how this mounts, I'm listening. Maybe it sits on top which is even more absurd but the screws that came with it wouldn't be long enough to do that? Maybe I'm just a moron and have no idea how that is supposed to mount. It would be great if there were some pictures online about this for reference but there is absolutely nothing. All red dots I have seen installed on these have been milled into the rib.
I was really hoping to get this to work because I found a picatinny mount that works with most red dots as it has a bunch of mounting patterns. It is made by Strike Industries. It is super super low. I'd need to modify it only slightly to work with the weaver rail but it would make the trijicon rmr sit very close to the rib for a better cheek weld. If you go with the rib mounted trijicon mount, it sits quite a bit higher than this. I think it's about twice as high. The last photo is the weaver rail with the mount to show how much lower this would be compared to the trijicon rib mount. Ideally, it'd be great to just mount the red dot to a custom plate so it's as low as the rib but that'd require a bit more money to do.