Center parking hang

No, it’s not impossible because it doesn’t require hooking that way. All you really need is a massive enough arm based on how far to the side your robot will be. If the robot is short enough on a side, you could even drive partially under the center platform and wouldn’t need a very massive arm. You reach sideways with your massive arm; then you push it down on the platform, raising your robot. Easy? Probably not. But impossible? Definitely not.

The real issue with this type of hanging is that your opponents can easily knock you off while you are hanging there in the mid air.

If you look closely at the field setup in the manual, specifically the platform definition on page 10, you’ll see “A close-up view of the Center Platform, with the polycarbonate structure underneath highlighted. This structure’s intent is to keep balls out from underneath the Center Platform per <SG9>; it cannot be used for Parking.” Thus making it impossible to get anything wheel sized if anything at all under the platform.

Tank treads?

If you push down with some arm, you’ll only lift that side of the robot. The only way that is applicable that I see is where you drive to the edge of the platform, and lift your wheels enough so that you can drive straigh up onto the platform, bypassing your alliance platform

What if you had a fold out platform that drops on the center platform, that your alliance partner would drive on top of, then you lift your robot up relative to your fold out platform. If your alliance partner is heavier than you, you will be suspended off the side of the platform, only touching the center platform. It would be sort of like a NBN lift in reverse.
The whole thing doesn’t seem worth it to me. If you want to get two robots center parking make a small robot.

You mean like the little tiny tank tread rollers? Those could possibly fit. But it would probably be pretty tight leaving very littler room to actually lift the robot of the ground. Also do you really want half your robot to be supported by those the whole match?

I would use omni wheels to drive up to the center platform instead of hanging.

Not if you maintain the shape of your robot relative to its lift.

When it comes to suspending something this way, volume of the robot isn’t the driving factor. The driving factors are build quality (don’t want things bending where you don’t plan for it) and center of gravity. If I really wanted to build something like this, my approach would probably be to build a small elevator (to go down) at the center of one side of the robot triangulated to the other side of the robot. The top of that elevator would have a horizontal slide with a huge pile of steel on top of it and a downward prong/stand. Drive that side right up to and touching the platform, slide the huge pile of steel with prong/stand out over the platform (moving the center of gravity of the robot beyond that side of the robot, over the prong/stand), and pull the elevator down. The robot would initially tilt a bit when the center of gravity gets outside the base, but that’s why I would drive it up against the platform; meanwhile, I wouldn’t design the prong/stand to start tons higher than the platform, so it couldn’t go far anyway.

I don’t think this is a good strategy. But there is a huge difference between not good and impossible.

Drop a flat piece of metal onto the platform before anyone else gets up there. Wait for your partner (or opponent) to climb onto the platform, thus weighting your metal down. Lift yourself off the floor using the now secured piece of metal.

Alternatively, (and I haven’t read the size extension rules, so this might not be allowed) extend a cover over the entire platform so that your opponents cannot contact the platform. Even if they climb up, they’re touching you… not the platform.

That’s true, I was just assuming that you were unable to shift your cg far enough away from the robot in any way that is possibly feasible