I would like to change my current filer (cartridge) to a sand filter. I am starting my 4th year with the current cartridges and they need to be replaced so I figured that now is as good a time as any to switch. The cleaning isn't so bad its just putting the filter back together is a PIA - came home one day and found I lost a couple thousand gallons of water cause the top of the filter wasn't positioned perfectly & this was 2 weeks after I cleaned the cartridges - never the less I want to switch to a sand filter
Here are the pools stats:

Pentair Clean & Clear Plus 240
Pentair Whisper Flow 1.5 HP - Single Speed
18,000 Gal
Run the pump about 10 hours /day

The current filter is rated for 90 GPM does the new filter have to meet this?
Current filter is 2" PVC any problem going to 1.5" connections on the new filter?
Was considering HAYWARD S244T PRO SERIES 24" any thoughts?

Thanks for any help you can provide