I use a WD-4 for my Ikelite Housing (G10) it works fine... one thing I have found with it is on the Dome it has 2 .030(approx) holes drilled into the black plastic at the 12 and 6 oclock
positions. Make sure that you don't press the WD-4 onto the port to far, and block these holes...if so,the water will not fill the void completely, and when you look into the LCD you will see water moving,so just make sure the holes are not being covered up by the dome on the housing.
A few other things,that might help... ALWAYS use a little grease on the inside "O" ring...It would be a good idea to install and remove the WD-4 several times at your house before you try it under water, it can be a bear to put on and remove!!!
Also DO NOT turn the WD-4 clockwise, or counter clockwise while trying to remove this...Mine was so TIGHT it turned the dome on the housing along with the WD-4.
Once I finally removed the WD-4... the dome on the camera housing was so tight I could not turn it with my hands...I had to use a strap wrench to remove the dome.
I was told by Ikelite that on some of the WD-4 domes... they did not make the grove deep enough into the plastic so the "O" ring was not seated far enough into the dome and it was a very tight fit to go onto the camera housing dome...they were "not kidding" it sure was tight,I also took some 400 grit paper and took a little rubber off of the "O"ring.
Easy way to remove is to : Place your finger tips against the housing and use you thumbs to push the WD-4 away from the dome on the housing. Sorry to be so long winded, but I hope this might help someone with there WD-4...Regards to all