good point. i drape over machine incl exposed rear fenders/wheels. only 4 tie downs on corners, works like a charm & far easier than anchoring a tarp. in addition, i leave hood up to discourage rodents as well. in terms of rodent mischief, i have found parking the machine away from growth & brush further reduces problems as rodents are cautious of open spaces.
in addition, don't think a vinyl tarp in contact w/painted surfaces does it any favors in the mid day sun. plus rodents are more reluctant to nest in a semi transparent compared to tarp. works like a charm, but i know a shed is far more favorable, working on that, regards
in terms of dimensions, i'd err to order a sun shade well over the tractor size