I know what you mean... you roll joints fatter than the rolled-up crutch, and the crutch sometimes slips out or is loose. Also, some people find it difficult to properly roll a cone-shaped crutch that fits their cone-shaped joints.
I try my best to size the crutch properly so it's just wide enough, sometimes making it a bit wider to err on the side of caution, since it's easy to trim a crutch that's a bit too wide when it's rolled up.
If I don't have time, I sometimes squeeze tight the paper around the narrow crutch, lick one side of the fold and try to adhere the paper to itself using only saliva which only works really well for certain papers. This makes the "filter"/crutch end of the joint nice and tight, narrower than the equally tight body of the joint that I put a bit too much weed in.