Wants to thank you for your help. I successfuly hard-plumbed my own Intex 15 foot pool 2 days ago using essentially the same technique.
In case anyone else wants to do the same and finds this thread, here's the fittings I used:
1. The connection to the pump input uses one of the nuts that I cut off the long flex-hoses that comes with the sand filter. I took one of those nuts, and dropped a 1 1/2 to 1 1/4 inch reducer bushing inside the nut (Home Depot had it). The lip on the bushing keeps it from falling clean through, and it's that lip which mates to the rubber O-ring on the pump input. I glued a 1 1/2" PVC T fitting on the back side of the bushing to hold the nut on. With that nut screwed onto my pump, the pump is now mated to PVC.
[attachment=2:17toazir]IMG_3609.jpg[/attachment:17toazir]
2. The connection from the bottom drain uses a standard hose thread to PVC thread adapter. I used Flex PVC line to run that back to my T fitting, inserting a valve inbetween so I can turn off the bottom drain input if I want to. That's all standard PVC work, and I used 1 inch line for it, since the valves and fittings were cheaper than 1.5 inch. I stepped it up right at the T fitting into the pump.
3. The connection to the skimmer uses my original lousy pump as an elbow. (Those Amazon adapters looked too terpermental) At Home Depot, I found a rubber coupling that's intended for use in drain lines (not pressure rated). Since I was using it on the input side instead of the output though, I guessed it would work. The hose clamps sealed around the end of the original pump, and a piece of 1.25" flex-PVC fit perfecty into the other side, which also sealed with a hose clamp. Viola - pump now mated to PVC. After that, I ran flex-PVC again back to my T fitting, again with a valve to control the flow from the skimmer.
[attachment=1:17toazir]IMG_3616.jpg[/attachment:17toazir]
Rubber coupling is here:
http://www.amazon.com/dp/B00077PW22, but cheaper at Home Depot.
Finally, here's a shot of the whole setup:
[attachment=0:17toazir]IMG_3615.jpg[/attachment:17toazir]
The pool input end I haven't tackled and don't plan to, since it works fine. However, I'm getting much stronger pump output now that I have 2 inputs (bottom drain and skimmer). I'm hoping the bottom drain will cut down on the vaccuming as well.
Thanks not only to TCJ, but others whose posts I borowed from. Without this board, I would never have attempted modifying any of this stuff.