re: Anyone use Smoker boxes on gas grill?

Just bumping an old thread, as I have a question about using the wood chips on a gas grill. I can get them smoking in the beginning by apying high heat, but then I need to reduce the heat for the slow cooking (in this case, to abouy 275 for some spare ribs). But as I reduce the heat, I lose the smoke. Any advice on this? I do the wrapped in foil method.

I'm to the point where I'm heating up other packets on my gas stovetop inside and then brining them outside and replacing the current ones. But still, the smoke only lasts so long (like 5 mins) at the lower heat.