Is it keeping it's pressure or loosing it? Sounds like you are going to have to install rim locks like we use on off road bikes to keep the tire from slipping on the rim when aired down.
She's holding pressure fine. This was probably due to cold day & cold tire. I think when the ambient air warms up I'll have the same hook-up at 30 PSI with no slip on the rim. The Diablos are even stickier when warmer.