The 300 is not a particularly slim profile watch. If one adds the Novonappa Nato, can you wear it under a dress shirt sleeve? Many thanks.
I don't own the SM300 ( well not the new one ) but I highly doubt it - the thickness is quite big ...I don't have the new SM dimensions but this is a pic with my Sub for comparison... These are lovely straps but they definitely add bulk However, It is of course possible to get your sleeves tailored a little larger to accommodate a bulky watch - most shirt tailors automatically ask if you need that these days ( usually 1/4 of an inch extra does it ).
While I enjoy NATO's from time to time, it's usually with short sleeves or with the long sleeves rolled up a bit.