HolyTrainer 2 small vs. standard sheath...

This is a tricky choice. My flaccid penis measures exactly 10 cm (3.9 inches) from the top and 6 cm (2.35 inches) from the bottom, following Thumper’s method on his excellent blog. So I have to decide: based on my measurements, the standard tube should fit almost perfectly. However, Thumper recommends a slightly smaller size for better comfort due to some compression. For me, the small HolyTrainer v2 would provide slight compression to my cock. Since this will be my first real chastity device, I’d appreciate opinions from you more experienced members of the community on what you would do in my situation before I spend $170… Best regards BottomBoy