from what some divers are saying the ike with the macro port can be a bit negative,i am looking at getting 2 ds125 and with 2 strobes it will definitely be negative ,don"t know if i should go with 2- 6inch arms per strobe or 1- 9 inch per strobe thats if the stix arms work on the ike ball joint
I have the STIX 9" arms with the jumbo floats and I also bought the Macro belt for my 100mm. They work great.
I have a Canon 30D in Ikelite Housing w/2 DS125's....yes it is negative, I don't know about any air bubble, mine sinks.
They have 1" ball joints just like ULCS so if that is the size of your clamps you'll have no problems. I'm going to buy more arms either the 4 or 6, haven't decided yet.
Good luck and I hope my comment helps