Hi Chris,
Its better to NOT solder crimp joints, otherwise they can become brittle. Using a proper crimp tool (ratchet style) will give a proper joint connection without the issue of fatiuge failure down the track. I wouldn't worry too much about sealing the mount with sikalfex, will be very messy and there is as much chance of water getting in via the plugs and then it cannot drain out if fully sealed. The most likley chance of getting wet is rain during the night when you have the kitchen out and something plugged in. If its not too late, I would suggest pointing the connections downwards, will minimise any rain getting into them that way.
I get back to AUS in late January, hopefully we can catch up soon after. We went to New Orleans for Xmas, then up to Memphis, so the Mrs could see Gracelands (is a closet Elvis fan) and then across to the Smokey Mountains, North Carolina so the kids could experience snow, just got back a few hours ago from the 10 day road trip and some 2,700 miles. Just 2 weeks of work left before we return.
Cheers
Mark