No problem.
A way to resolve the size issue would be to pinpoint who you feel the early adopter for this might be… For example, of it is the silicon valley male, maybe just make the men’s watch.
Also, design research much more about what people do than what they say. Sometimes we go in and ask a question, like “what size would you prefer?” and then casually ask “wou,d you mind if we measured your watch?”… I bet there was a discrepancy between what they said they would prefer and what the size of their watch actually was. The second is more important because it gets to what they would actually choose to live with vs what they think is the right answer. You could always repeat the exercise. I’m not surprised how many people were wearing watches, it is a popular blog story to say people aren’t wearing them but they remain a tribal indicator of status in our culture.
If you want to use an off the shelf strap for customization, a solution for both the attachment of the module and the customizable strap is the NATO strap. They come in a lot of widths and colors and only need two bars to slip under. If you design a double of bars or slots into the underside of your module you should be all set.
http://www.fusiongear.com.au/traser-traser-nato-watch-strap-black-22mm-p-443.html