Here is a picture of one of my standpipes. You can see the floating buoy which is seated inside a 1" strainer which in turn is surrounded by the large sponge.
The buoy rises/falls with the water level. The strainer sits in a 1" PVC collar.

Since the strainer is 1" and fits into a normal PVC collar. I just added the extra PVC length and a new collar and extended the pipe. You can see that the waterline is only 1-2" from the overflow teeth.

The PVC and collar directly below the sponge is the EXTENSION. All the rest was there.

Only two pieces of equip:

1" PVC cut to desired length.
1" PVC slip collar.

I cut a few different pieces to play around. Had to buy 10' of PVC whch will most likely last me a lifetime. Let me know if you need any lol

Let me know if this is unclear.

Hope this helps!