Yeah, you want those rubber snubbers very tightly pressed against the tire sidewall on the spare, otherwise you can do some serious damage to your tailgate.
What most people do to extend them is get longer bolts and stack hockey pucks (with holes drilled in the middle for the bolt) or cut little sections of PVC pipe to put between the tailgate and the rubber snubber.
Hopefully this makes sense.
For mine, I actually got another set of rubber snubbers and cut the domed portion off the top, then stacked them. It worked nicely and looked factory.