With the Wilton hidden tiers deal. The 8 in. cake would be on an 8 in. circle cut to size, but then I would to place that 8 in. round on top of the wilton cake circle thing (you know, the hard white one you can buy in Michaels) with the hidden pillars. I know they sell 8 in. ones but you can still see a bit of the white part, so I was wondering if you could go smaller since the top round would be on it's on 8 in. board (and I have carpet tape to put on the wilton circle to hold the 8 in. round board/cake in place.

Would that work?

sure will