Better footing...
Tim, if it works, no worries, why add weight? I don't know about you, but the rear floor in my RV4 was underneath the back seat. The floor under the front seat is attached with screws. I removed mine and installed rear passenger footwells exactly like the ones Bill pictured above on either side of my front seat, aft of the spar. I used plans from a 1989 RV8R magazine article from a builder. You have to be careful of the depth as they will interfere with the aileron pushrods. Other than that, they are highly recommended.
An ever cooler (or warmer) mod I saw in a -4 at a fly-in was holes drilled into the front of the footwell with heat ducted through the holes. using 1" scat through the spar extrusion hole where the front stick access travels. Very slick. The HR2 floor is designed with extra room for the rear seat pax's feet.
Smokey
HR2