You guys have brakes for the passenger?! Not me, saved a bit of weight and eliminated the need for a passenger preflight briefing, same with the rear throttle. The most I do with a passenger is let them handle the stick and rudder, and they're damn lucky to be able to do that
Not a super cub, but a RANS S7-S, my "forward cargo deck" is a piece of aircraft plywood about 3/16" thick, strategically oriented with the grain to provide stiffness where needed. This grain/stiffness helped me to be able to go with overall thinner plywood. 2 main runners, 3/4" x 1.5" are screwed and Gorilla glued to the bottom of the ply, on the same centers as the seat attach points, they were made from my 1946 T-Craft spar remnants, so they are clear spruce (and have good mojo). That's the rear support.
The front bears on a telescoping aluminum tube, with a center support, the spruce runners cup the tube, half circles in the runner match the tube's OD.The tube is supported on the side longerons by two short stubs of 4130, that the tube slips over, they were welded in as I built the plane, as I had done similar on my first S-7 and it worked so well I did it again. The telescoping tube has a pip pin so once engaged to the side stubs, it stays there. When I take a passenger I take it out, in about 10 seconds, I have forgotten a few times and unless the passenger is quite large it is not a deal breaker as their shins are underneath it. two mid point supports (so it's supported in 3 places I guess) have tabs and more pip pins, so the deck pops out in seconds.
The stick stub, machined to match the ID of the removed control stick, is underneath the deck, so no further stick stub protection is needed, the deck is it. The pic is of it in use, it's stout enough to hold a persons weight, the notches are so the door latch clears. One nice feature is there is about 6 or 8" of room between the belly carpeted fabric and the deck bottom, making a good storage area for stuff I usually won't need ready access to but still want to haul and be able to get to at the end of the day, when the deck is usually cleared already. I find that several sub divided areas better for gear storage, rather than in one large junk pile. It's perfect for carry a large cooler with a couple cases of beer, (did that one time) and the seat belts are accessible and are used for their purpose. Also a large tee pee (folded) that I once airdropped to some backcountry skiers simply by opening the door and side slipping, as the deck is about even with the door sill. The deck and the main baggage area further aft gives me about 5' of cargo space,with a center bulkhead, pretty good for a plane this small.

After taking a closer look at Vmc's fine work I hesitate to post any further pictures