I play with both possum board and a stand-up stand.  If you play with a stand acoustically (not amped) you will want a board underneath, as the greater sound will head for the floor if you don't.  If you're playing with a pickup I don't think it makes much, if any, difference.

My stand-up stand is a tall waiter's tray table, from a restaurant supply house for $28.

I am considering a couple of things at the same time.

Had thought about modifying a keyboard stand to make a stand to play lap dulcimer in standing. Will I need a board under the instrument like a possum board or just a support for the tail and head block?

In regard to a possum board for playing while sitting, is there an advantage to the board itself or will a frame like support with support at the head and tail blocks be as effective.

Need your thoughts from those who have tried different things.

Thanks