I want to fit 6.5 components into a 6x9 spot on a grand cherokee, then make adapters for the 1inch tweeters to go in the stock location on the dask.

Would adapters like these on ebay work well? I have heard plastic is not good material to mount on. The only alternative I could think of would be putting a layer of deading on the plastic for the speaker to mount into or making mdf adapters.

How much would it cost to make mdf adapters? I do not own a jigsaw but could probably borrow one..