[6pack] Max tire size for rear tube-shock upgrade

[Douglas Morris]

Im gonna need new tires soon, and Id like to make that purchase compatible
with the kind of tube-shock upgrade kits that bolt into the original shock
mounting holes.
Unfortunately, I cant find any info about the max tire sizes allowed for that
option.
(Yeah, I found info on the body-mount option, but not for the simpler
direct-replacement option.)
Any advice?