Nice finish. beautiful furniture, and it would help keep the plastic from rocking around when one treats it like a real piano. Yours has the same problem the one my high school friend built for his yamaha 88 key kb. You've got a vertical wall right behind the back of the black keys, with the handles projecting out over them. I found I was banging my fingers into the wood while trying to play. He unscrewed something and I finished Pictures at an Exhibition. My Steinway console has a bar 1/4' higher than the back of the keys, then back 3/4 " to the key cover vertical wall.
I'd easily pay $50 for it,
I said $250 from a business standpoint. No matter how gorgeous it is, if I'm spending upwards of $250 for an accessory for a digital that takes up as much space as an upright, I'll take the upright. Plus it gets rid of the portability of a digital, unless it can be taken out quickly (doesn't look like it if the cords run through the wood).