The voltage range for the RasPi is 4.75V to 5.25V. If the test point are between theses figures it will work just fine. In my experience in back-powering, the length of the upstream cable, has a lot to do with the voltage seen at TP1/TP2. I also suspect high loss at the connectors on some cables. If you see voltage under the 4.75V then try a shorter cable.
I have had a Raspi work just fine as low as 4.25V. Usually what will not work at this low voltage is a USB device plugged directly into the RasPi. And though you are powering your RasPi on the wrong side of F3 your hub should have its own protection.
Overall, I have been back powering a modified ver1.0 since August 2011. No problems at all. I have just setup another RasPi to back-power through a hub, a ver 2.0. It works real well also.
You should have few problems as long as the voltage is in the right range. There are quite a few people running their RasPii this way without problems. Give yours a try for a bit. It does reduce the wiring attached to a Ras Pi by a little bit.
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