Ok here's what happened.
The installer showed and had his own idea of how to make it work.
He hooked up a Zinwell unpowered 3x4 MS to the existing 5x8 and connected the Tivos to it. That didnt work, the Tivos (model R10) failed the test of the satellite receivers, not seeing all of sats/transponders.
We moved the Tivos to the 5x8 along with HD receivers. The 3 "regular" receivers were put on the 3x4. That does work. That leaves me with 1 open connection on the 5x8, and one open connection on the 3x4.
The install is far less complicated (and less failure prone, I hope) than the proposed (4) splitters and (2) 5x8's, and works. OTOH, I wonder if this will continue to work in the future. As long as the regular receivers only need the one SAT (101?) I guess I'm ok.
Getting the Tivos dialed in was the most troublesome of the entire day. D* needs to do something about making that painless. The installer hung around for about 40 mins trying to get them dialed in and I finally just released him and finished it up myself later when they finally got through.
The whole thing, 2 wall drops, 2 Tivos, 3x4 MS, and trying to dial in the Tivos took the installer about 3 hrs. He did good work on the cabling and wall drops and outlet plates, even repaired a couple of poorly done connections from installers past.
All in all, I'm pretty happy, now if only these Tivos were not so dang UGLY!