The top mounting rail on the Fobus M44 handguard
sits slightly lower than the rail on the AR flatop upper. I'd like to know is this irrelevant? CanI  still mout sights on the forward top rail?

I've never used the Fobus handguard, but from what I have seen, it doesn't seem stable enough to mount optics on it's rails. If you want to mount optics forward, try the SIR or the RAS II. Both cost significantly more than the Fobus, but they're worth it.
Hope this helps.
Steve.

All things being perfect the top-rail of the handguard should be on the same plane as the flat-top rails.

SMV is correct though, as the handguard is susceptible to movement by many factors, (one being the pressure excerted by your own hand) it cannot be counted on to be steady enough for optics to be mounted on it.

That said an easier, less expensive way of utilizing the M44 (other than the SIRs or KAC RAS II) would be to place an ARMS #38 Super EX on it and mount your ML/ML2 (w/ARMS #22M68) to it. The Super EX should slip over the rails of the handguard and as it's attachment point is the flat-top on your upper should be entirely secure. This set-up should co-witness w/ irons and you'll have the #40 which is built in to the #38 for your rear BUIS. ([url]http://www.armsmounts.com/list.html#38"[/url])

Mike

M44 is fine for forward grips or lights.  I wouldn't mount any optics on it.