Hand ascender attachment to harness.
Hey, Old Irish, Tim here. I'm a relatively new climber myself, so I may be able to relate to you more than most. Since I'm so new, take what I say with a grain of salt. I have the same harness that you do (mine is the older version). I like to use the four foot long version of this item from TreeStuff.com.
http://www.treestuff.com/store/catalog.asp?category_id=21&item=1860
Those dyneema slings are almost as strong as the thicker slings, but much thinner and I'd guess lighter. I use the four foot sling and just pass it through the handle of my hand ascender, so that I can roll my body right or left and the sling just slides over the handle and keeps my weight centered. I have attached a triple-locking carabiner to each of the side "D's" on my harness, so I just clip each end of my sling into the two biners. I also make sure that I clip a biner into the top of the ascender once the rope is in it, just to make sure the rope doesn't roll out.
I'd be interested in seeing a link to the Petzl suspenders that you use. It doesn't happen very often, but it would be nice to know that if I happen to roll forward during a climb that I've got a harness/suspender setup that absolutely will not permit you to be dumped out of your saddle. I'm not there yet with my setup, so I tend to want to have connections to my rope that sit fairly high above my head, but still within reach, and tied to my side "D's". This makes me feel as though I have no chance of pivoting around the hip axis and dumping out of my saddle, which is what I'm looking for. The down side is that when you take off your foot ascender and remove your foot loop from your hand ascender, you can fairly quickly feel uncomfortably squeezed at the hips by your harness. I accept that trade off, and just try to keep the time periods without foot attachments to a minimum.
This is another piece of gear that I use all of the time, and it sits above my hand ascender. I absolutely love it and trust it with my life. It has the advantage of being a cammed ascender also, so no teeth to tear at the rope. It's not obvious from the ads for the device, but it has two separate holes into which to slip the quick-release pin, which allows it to accommodate a wide range of rope sizes. It's a thing of beauty, and I can't say enough nice things about this product.
http://www.treestuff.com/store/catalog.asp?category_id=193&item=144
That's all for now, if I think of anything else I'll chime in again. Best of luck.