The OP (Ratbob) posted that the bikes had stock headers and slip-ons. Anyone with a heat issues on a Twinkie needs to take three initial steps.
Dunno if it’s a misprint or not but there are a few s&s cams with unusual exhaust specs but they seem to usually work well if added to the right combination of parts. Have a look at the specs on their 635ho cam. It’s very unusual
What state/city are you in? We can try and find you a good one. Go with the tuner they want to use.
Melbourne
Eastern Big Twin in Pakenham are a sponsor, they tune with PowerVision, you would be looking at about $200 for the licence and about $600 for the tune, don't quote me on that but that's about the going rate, if you want to go a bit out of your way Lushy is in Victor Harbour, he does a top notch job.