I can this RIS for $200 locally. Is the RIS sturdy enough to mount sights  or should I save for a newer model?
I want to mount an aimpoint on my colt 6520 to cowittness with the irons, what do I need?
Thanks for any guidance here

If you want to mount an optic on the forward rail Your best bet would be a stable Freefloat.
The Knight's FF RAS, Larue, DD, come to mind.

FWIW-It would be a better idea to mount the optic directly on the rec. flattop towards the end with a BUIS
to balance the weapon out better and still give you a excellent peripheral view.

Pass on it and grab a LaRue.

Put it on EE if all you want it for is optics and VFG.  Get a RASII or one of the other freefloat tubes.  For what you paid you should be able to turn it for the same price and pick up an RAS II for maybe $10-15 more.  That'll freefloat it, and you can mount the optic on the hump or over the barrel.
Or don't worry about it and get a cantilever mount and run it off the front of the receiver.