Initially I was looking to buy one of the tri-rails but found that it has been out of stock for awhile.
After trying out several AR accessories I had laying about, I discovered that vent holes in the upper handguard interface perfectly with M-LOK, you only need to take a small round file and remove about 1mm from each of the leading edges.  Utilizing this, I attached a QD M-LOK Magpul part no (MAG606) swivel on the left side of the HG.

The Surefire Scout light took a little bit more work but fit almost perfectly after some mods.  I had to remove the same 1mm from the vent holes and in addition, I took about 1/8 of an inch off the upper right corner of the top handguard with a sanding block to allow for mount clearance (approx 15 mins of sanding).  The mount I used is the MAG935 extended cantilever mount.  With the small amount of material removed (circled in red below), the light is tucked in as close as possible to the handguard and gas block and is positioned perfectly so that it does not impede the rotating gas valve or the handguard retaining pin.

To mount the SR07, I utilized the Magpul MAG 617 Tape switch mounting plate.  I ground off the M-LOK posts and attached the rear screw using Magpul MOE hardware through the rear vent hole and drilled a hole in the front to mount the forward screw also using MOE hardware.

With these mods the T91 becomes effectively as good as most modern western carbine setups with the exception that it is not free-floated and there is no provision to mount night vision.  Although it took a bit of work and experimentation on my part, I feel that this setup is superior, aesthetically and ergonomically to the Taiwanese quad rail/mlok or tri-rail solution.  Utilizing a thumbs high grip on the front handguard there is sufficient sling clearance and the light switch is in the ideal position.

Awesome!

I ordered my upper. Wanted the 14.5 barrel, but it was out of stock.

I'll be mounting an Aimpoint PRO, and it will be my truck gun for the time being. After reliability testing, of course.

Good shit.

I'll have to go through my sights box. I want a fixed rear sight to complement the PRO. I think I have a leftover Daniel Defense, but if not I guess I'm ordering another one.

Any issues with handguard after attaching the QD sling mount.

Looks good