Optics on the handguard?

Has anyone here mounted optics on a freefloat CAR hanguard? Are they stable enough?

Just curious as I'm happy with my A2 sights on the carry handle, just wondering if anyone else has mounted a red dot or other long eye relief scope FOREWARD of the carry handle to co-witness their irons.

"Scout" style scopes are mounted onto the barrel or a rail. AR forestocks are too thin.

I'm talking about replacing my front handguard with a free float tube with mounting rails built in.

A decent free float tube or rail will be just fine. Hell, most of the US military is mounting their PEQ-2s and 15s that they use for aiming with nightvision on non free floating RAS systems and that seems to work out for them.