To answer your questions/comments in the order you typed them...
1) we have no product that allows you to network the Pioneer 810H, nor is it possible to extract programming from units that has already been recorded. There are ways to extract programs by installing certain hacks (discussed on these boards, but not provided by us), but the programs have to be recorded AFTER the hacks have been implemented
2) the Pioneer unit can only hold one drive.
3) InstantCake only allows you to build the equivalent of a replacement drive kit - it does NOT contain any networking functionality. PTVnet creates networking functionality and that is a separate product and is only available for select DirecTV Series2 DVR's and the HR10-250.
4) Even though your Pioneer unit is at a later version, it does not matter than the version used for InstantCake is 7.2.1 - your unit will update to the latest version its eligible for when it makes its daily call.
Please see the links below and the product descriptions for InstantCake and PTVnet as that should get you on the right track.