I have been pondering it for a long time and spent lot a of time staring at my setup wondering how I would do it. Following are some pics. I will post later with a parts list as I did it a bit different from how some others have done it. I got the box adapters at Lowes but it seems they have changed the part number. The link someone else posted shows that the part is no longer available.
The suction port and return are both Hayward. They fit perfectly in the holes I had for the large Intex plunger valves I had. No need to modify and I had minimal water loss while swapping them out. I wanted to have the better fittings for standardization purposes and also to avoid 2 more box adapter work arounds.
I decided to use rubber L connectors instead of unions because it was easy and it gives me some flex to make up for alignment mistakes. You can see the R-Max foam board peeking out from beneath the pool. Yes, I know I should have used the pink extruded foam, but the 2 stores I went to didn't have enough and I was going to setup THAT day, so no time to keep looking.
I chose to use a sweeping T to join the suction port with the skimmer rather than a regular hard 90 degree T which theoretically causes less disruption.
Close up of the skimmer piping. If I do it again in the future, I would search for valves with slip fittings rather than threaded so I could have avoided the additional fitting on either side.
Close up of the return piping.
Close up of the suction piping.
The pump side piping. This is the only place I had to do the box adapter fix. I used long 90 degree parts instead of hard 90s hoping it would be a little less head pressure.
Having a standard port lets me unscrew the strainer and use the standard vacuum adapter. Now I don't have to use that skimmer adapter that came with the Hayward skimmer. That is nice!
The whole Hayward setup. Suction port on the left, skimmer in the middle, and return on the right.
It's just crazy how much more flow there is. This little project made it totally unnecessary for me to consider upgrading to the 2650 when this one dies. It would actually be too much. As it is now, when I stand on the opposite side of the pool the circulation current is strong enough that I can feel it brushing across my calves. I changed the eyeball from pointing as far left as possible to a little closer to the middle of the pool because it seems that the circulation is too fast and things look to be going right past the skimmer. Pointing more towards the middle seems to be better. Why would I want to spend more to run a .9 hp 2650 when there is this much flow from a 1/2 hp 1600? Ok, more time between backwashing but when the water is well balanced there isn't that much being trapped so I don't feel burdened by my backwash schedule.
This picture shows the eyeball pointed as high as possible. Before the mod the flow would disturb the surface about an inch but not actually break through the surface. Now it is much higher!
This picture shows how much turbulence there is now. This is with the jet pointing horizontally (not up like it is in the picture above) and nobody has been in the pool for a half hour.
I'm so happy that I finally got around to doing this. The first section I did was slow, but now I'm really quick at it. It wasn't scary at all and I enjoyed doing it.