K
I always thought the 45.5 on rubber and 42 on steel make a nice combo.
I have a 7in wrists and I have found that in my particular case, the UPO size can vary wildly depending on which strap/bracelet you use. Here are my findings:
1. On regular bracelet it wears just on the limit. On bracelet it is a huge chunk of metal but because of the way the bracelet drops, it is ok on the wrist.
2. On sports rubber (rep rubber) it actually wears pretty strange. The rubber extends for a bit parallel to the watch thus making the lugs "extend". On my 7in wrist, the rubber does not wrap the wrist, on the contrary. There is a hole between the skin and the rubber big enough to put my pinky in. I think that this combo needs a bigger wrist than mine.
3. On leather it wears ok. Looks smaller than on bracelet. Same as bracelet the leather drops down as you tighten the strap.
4. On NATO it looks fantastic since the NATO strap wraps snugly the wrist.
5. The winner combo IMHO is to use it on the new omega rubber straps. The strap is angled completely perpendicular the the watch so it wraps around the wrist. I think is is designed that way to solve the issue with the regular rubber straps.The problem is that they are expensive since they haven't been repped yet. This is the combo I am using for my UPO (see pics).