Hubbies BP isn't constantly high, it fluctuates quite a bit depending on stress levels etc. It is significantly lower after I give him a massage for example. He still hasn't really gotten into the inverting yet, but I am working on it.
Since my hours have increased at work, I am now only inverting twice a day, still for around 10 minutes, although I don't really time it, just go with the flow. Sometimes I only slightly invert and take a little nap. It's very relaxing.