Not much I can say bout this sorta' stuff, except thinking shortening up your track width would increase the angle the struts are at, too wouldn't it? That might effect their durability.
There's a couple places I've seen sidecar folks at where you could get some sound advice/bump heads... SNOWCAMP for one, CSR (in May) for another... There's a few folks here in ADVland that live nearby too - might try pinging some of them in PM's - haven't met a "bad one" yet.
If you want to try my rig you're more than welcome to bomb around the MSF course behind South Sound Sears - that'd give you some comparison at least, to what your rig handles like versus something a little narrower (like mine).
Seeya' Tuesday - "First run of the New Year"