For a SWiM install you only need a single cable for both tuners in the DVR to work so it's much simpler than either way you described it.
You'd use a two way splitter in the attic and it would still need to be power passing. The power passing leg would need to be routed to the basement with another 2 way splitter and then the power passing port on that would need to go to where ever the Power inserter is with one DVR behind the PI. The other port in the basement and in the attic would go to their respective receivers.
That sounds like a possible approach. Need to get the SL3 SWM, Power Supply, and a power splitter and work from there. Saw a package deal on eBay for a brand-new setup:
DirecTV SWM SL3S 3 LNB Kit 21v Power Supply, 4-Way Splitter for $59
I don't have the plan mainly because the last time a DTV guy came he slid off my roof , and then told me the trees had grown too tall since I had the original old round dish in the '90's. So I got a local authorized private guy to put up the SL5 and aim it. The trees keep growing and I can't move my house LOL, but I emailed him the signal stuff posted above and he texted me back saying he's going to try alignment, plus maybe use a tripod to elevate and stiffen the mount. He does a lot of commercial stuff, and is all over the region doing that. Private homes are maybe 20% of his business I think he said... so I just have to wait until he gives me a date & time now. But he's definitely coming in October.
UPDATE: My Dish guy called me last night and he has all the SWM stuff I need in his truck, so its just a few days until we can coordinate our schedules and hopefully my problems get solved and all my DVRs work.
Edited by pocolocobob, 21 September 2012 - 10:51 AM.