An update of my own investigations.
The parts man at Melvin Rutter says that the chassis rollers are intended for earlier Morgans before rack & pinion steering and couldn't comment on whether they would help. If they did help I assume that it would be at the cost of reducing full lock to some degree.
I also visisted the factory shop for a couple of items and spoke to a mechanic. He was more forthcoming and was surprised that there was contact and suggested two reasons:
- there is not enough toe-in
- a third party accessory that's too long (factory BRBs have oblong holes so they can be jiggled to avoid contact)
My thoughts are that the toe-in might be wrong because SSL suspension was fitted at the same time; and I don't know who made the BRBs.
The mechanic then suggested a simple solution is to flatten the end of the bar, cut off the old end piece then drill new holes in the bars and chassis. This would give bars angled further forward but with some reduction in their bracing.
I'm now pondering whether to attempt the work myself.
As an aside, while at the factory I saw a new Plus without its body in the open garage near the spares shop. It had both top & bottom braces to the kingpins; it also had Spax dampers on the rear & a panhard rod so I guess these were all options chosen by the buyer. (I didn't have the nerve to turn the steering wheel to full lock)