2 quick questions.

1) No
2) No

you'll be busy for quite a few yrs removing small stones! -not a problem.
petrol will osmose into metal of can over time to a small degree, is a problem when people cut open fuel cans/drums with torch or grinder and bang! bottom line is the remnant amount of petrol is tiny and its a very doubtful problem to diesel engine.
MG.

Thanks for the replies guys, as expected not an issue but thought there may have been something I hadn't thought of. I'll just be removing the stones that make the annoying ticking while driving on the hard top. Cheers

Only problem with stones is if the SAME one stays there for a long period it can be driven further and further into the tyre case.
If the same tick is there for a long period then I would flick that one out, but generally they remove themselves during braking, cornering or general tread squirm and are no problem.

Mostly the ones which stay there are TEK screws.