Hey there laptop
there is a pic of the type of fitting to go through the housing
at the bottom of this page
http://www.pcmus.com/Dive-Photos/Dive-Light-DIY-SCUBA.htm
as for your umbilical,
attach the strength member at the tow/balance point (hose clamp? eye bolt?)
Make sure you have plenty of slack in your cal5 cable
we use 11-12ft of hose/comm cable for every 10ft of strength member,
electrical tape the lines togeather every couple of feet with a little slack
to your cable the whole way.
that way if it ever gets hung up on the bottom, (hopfully in the rigging of a 300yr old ship)
there will only be strain on your strenght member
also leave some slack right at the unit so there is no way for the cable to be pulled out
of the housing from any direction.
in this pic you can see the eye of the strength member and also that the co-axe cable's slack is being
held out of the way, with a strap that will break long before there is damage to the cable
http://www.rentarov.com/webpics rov/pages/rov with wreck6.htm
we use this for divers and can pull a man, his gear and 60lbs of weight over the boat's gunnel
with his umbilical alone
hope this gives you some ideas
B.C.