37 Spare tire cover --oversized tire?

[mumpsimus]

My new woodie came with a nice spare tire cover and a band. The tires are 6.5x16" bias ply. I've tried to get that little keyed latch to grab the spare tire bracket, but cannot get it to hook on. Is there a trick? Or will it just not fit with this tire size? Even without the band, the cover doesn't seem to fit.

Thanks
Pete