Rear speakers for '65 Ranchero?

[beerbelly]

I used a piece of 1/4" black Sintra, a plastic material we used in the sign business I retired from. I found that a McMenamin's beer coaster fit nicely inside the tube, so I traced it & cut it with a jigsaw, then cleaned the edges up with a sander. I pushed it into the tube until it measured equal from both ends, then marked the center in 4 spots around the tube for screws to attach it.