I've got a 350D, Ikelite housing, Ikelite tray, arms & grips with 2 DS-125 strobes.
I too never use the lead weight.
With the 6" dome, I find the rig weighted nicely as I almost always shoot with both hands olding the rig from the grips.
In macro mode with a small flat port, I find the rig a touch heavy, as I often need to brace myself on a rock (due to current). It gets a bit difficult to hold the rig with one hand and get composition right, especially after a few shots.
To compensate for this I've used some pool floation toy called pool noodle. It is basically a long cylinder of foam that is mega bouyant, had have two six inch lengths on the strobe arms. This is not the greatest solution however as it does compress with depth and thus becomes increasing useless as you go deeper.
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