Yes, the topcase blocks the beetle's lids. Must move the topcase back slightly or off each time.
JCW, about 45L.
I did have that concern during installation, so I used industrial strength hex bolts, forgot the grade. Then had them extend all the way through the subframe an extra ~.5". Then used a m6 and m8 nylon thread locking nut on each of the two bolts on each side to ensure they don't back out and don't strip out.
So far, 800 miles on that setup, most of which loaded with luggage... all is well.