I think the combination of these two (undressing only as far as they want and offering the towel) both leaves plenty of comfort to grasp onto for those who want/need it, and also offers room for guys like you to be fully naked. Great advice. Thanks!!
For me, the most neutral way of handling the issue, as the OP has already starting doing, is to be instructed to undress to my comfort level and be offered a towel if I want it. My own preference is to be uncovered and usually drift off a bit, which must mean I am comfortable.