by 3M clear bra tape and cut to fit. cost about $15 for enough material to cover both tops. got mine from stickercity.com. same tape we use on helicopter leading edges in the desert. nearly invisible and easy to replace if damaged. have had it on my RK for three years.
I have the HD covers ans they work great, no marring or damaged paint. Just put a couple of good coats of wax on before you put on the covers. Had mine on all season and never took them off until winter storage time.
I've had the HD lid bras on for two riding seasons,approx 15000 miles,I take them off occasionally and wax the lids....no problems yet with paint,they fit great,and I like the look.