Speakers keep moving

I posted one up here a second ago about ballasts, and I also have another question. I have the Bazooka Tubbies 8 inch on each side of my tower and they keep moving on me with vibration and wind. They are tightened down to the max, so I put so no slip matting inside of it and it doesnt slide as easy but it still slides. What are you all using to prevent the slippage.
Thanks!

Looks like you have them mounted to the vertical uprights of the tower? If you mount them to the horizontal top of the tower, they won't slip down. Most of the speaker applications I have seen are mounted to the horizontal top of the tower and not the vertical uprights.

Yeah, I wanted to mount them on the top but I can't because of the bimini. It covers the entire top, the only way would be to cut the bimini or take it off...
I was thinking maybe a set screw, but thats all I can figure would maybe work, but thats another hole to drill in the tower, ug...

A friend of mine has the same problem. Thankfully the no slip pads helped out a lot but they still slip. I dont think there is anything to prevent it and just push it back into place when they slip too much.

Have you considered some sort of cement/epoxy??

Yes, but I am debating on keeping these or moving to the bazooka's with speakers on both sides...but then I have to upgrade the amp...Ive got a kenwood 300 watt just to these two speakers. My big fear is I won't get them aimed right before the cement/epoxy dries, or If the bolts inside that aims the speakers up and down comes loose...guess I worry too much