How much room must one have in the pants to actually carry like that?

Personally, with the current crop of full size weaponlights i find AIWB carry with a light to be the most unrealistic of all carry methods.

For me, i carry my pistol essentially right over the hip flexor. If i attach a light i lose mobility of my right leg. I cant climb, i cant bend over and i cant crouch.

If i move the pistol more centerline towards 12 o'clock i have a pistol muzzle resting on top of my privates...

The closest workable solution are the Crimson Trace Lightguards but even then, its more bulk in an area where there is VERY little room.