Rockshox REBA Team

I've got Rockshox Reba set at 100mm and 150 psi in both chambers which corresponds to my weight - the performance is good and the sag is fine - rebound ok. But when I get off the bike the fork doesn't extned back to 100mm - just to about 85-90mm. I've read the manual online and I can't find any previous threads - any ideas?
2015 Cervelo S3
2016 Santa Cruz 5010
2016 Genesis Croix de Fer
2016 Santa Cruz 5010
2016 Genesis Croix de Fer
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Inbred
2016 Santa Cruz 5010
2016 Genesis Croix de Fer
This guide may help:
http://hometown.aol.co.uk/peterpoddy/RSairpressure.html
2016 Santa Cruz 5010
2016 Genesis Croix de Fer
But TF Tuned recommend running higher -ve pressure than +ve by 10-20psi depending on rider weight.
I tend to favour the 60% method and have no problems getting full travel and good feel.
I've heard of cases where Rev dual airs have dumped air across to the -ve chamber in use though, and kinda stuck down.