I can't speak to Sage chassis, but when I was looking into scope mounts, I ended up going with
Sadlak Airborne scope mount. I settled on this, because it has gotten the most consistently positive reviews and user posts on sites like this one [search yields many pages of results with some good contributions] ...or maybe more accurate to say that "Sadlak got the fewest negative remarks of any I saw." Bassett was the other company that got lots of good reviews.
Regarding some general notes from my pre-purchase research there were some people who said that their aluminum mounts didn't hold up to lots of rounds the way shooter had hoped. There were also people that said that mount x or mount y didn't allow for iron sight usage. Others said various mounts just weren't as solid as had hoped. etc.etc.
So, I'll just include some Sadlak mount +/– remarks from my experience.
The + list: solid as all hell! (this thing has never budged after many cases of various ammo have gone through my M1A Scout); after initial setup, no tweaking/tuning or re-tightening has been required; lots of contact points at good locations for good solid support; very nice installation instructions; no irreversible modification of rifle required (uses strip clip guide); iron sights viewed through deep groove running down center of rail; nice height for comfortable shooting; no problems getting in the way of ejecting casings; honestly, I could wax on for pages about how much I like it, but I think that's less helpful than mentioning some of the [rather minor] drawbacks.
The +/– list: installation is
reasonable but not necessarily
easy (it requires you to level things properly, use appropriate torque settings, etc.); while there are restrictions regarding receivers out of mil.spec. there is still some adaptability that the mount has to mount to out of spec. receivers within tolerances (not a problem I ran into).
The – list: You gotta drop some $$ for it; it noticeably adds weight (airborne is better than original and titanium is lighter but even more $); this is
not what I would call a low-profile mount (cheek riser required on standard stock, but not for my current setup with Blackfeather + AR-style tube stock); I would not recommend removing the mount after it's on (you
can do so relatively easily, but due to the way the cam lever engages the receiver and precision of installation, I would assume you would only get to pop it off/on so many times before things loosen or something ...but that's just an assumption); while I can use the iron sights, lining up the sights within the groove very
marginally slows target acquisition (I don't even notice now, but I remember I initially did).