I will be able to report on the 60D as soon as I get mine which has been on order for > 1 year. The longest "gestation period' yet for a Seacam product. The 60D shares many of the "pro" features of the previous Seacam D series underwater strobes none of which are shared by S&S strobes such as S6 fitting, battery indicator, super wide dome, and metal build. I have a couple of S&S 250 strobes as my basis of comparison. I have not even seen a YSD2.
Glad to hear to worked it out. Very easy to jamb controls on the inside - I know from experience. I have a fair amount of loose remote control cable in mine so have to always be on the lookout for this issue. Taking blank shots is a good idea too especially now that we are not burning film frames. BTW I have had DUI dry gloves leak on me. Put on a brand new glove and still had a leak. So when I bought my fourth (since 1980's) drysuit a few years ago I decided to say no to dry gloves altogether.
I have gone both ways. The shutter release AF-on is quicker so I find it better for getting fish that are on the move - I may use servo AF as well for this scenario. The rear AF-on button works great for non mobile subjects where one may want to focus carefully then leave it there (AF-S mode) without having to resort to the AF lock button.
I prefer to use 5-finger neoprene gloves when coldwater diving such as in B.C. for better dexterity. I have been through various dry glove designs and decided it was not worth the struggle, leaks, and accidental removals while under water (The Vikings were especially good at that!).
60mm was my "go to" focal length back when shooting DX. However I found the 105 useful too. Especially for smaller reef fish, e.g., those < 10cm (4") in length. Here is an example: http://www.salmonogr...raits/i-DB7S5Gd
This shot was challenging but I managed with the older tech AF in my D2X. This might be a piece of cake with the D500. In general I think that focal length should be inversely proportional to subject size for UW portrait shots. Looks like you already have the lenses you need.