Above ground

[wildchild61]

Can you make 21x4'8 round pooI to a 24x54 pool

 

[TinFoilHat]

There would be way too much work involved and the liner and additional parts on top of a used pool already would probably not work out.

 

[dereksanders]

My guess is you’re trying to fit it to an existing structure/deck. One could do it with the appropriate material and equipment.

 

[Mdragger88]

This question needs some clarification.
Are you trying to modify a pool (not recommended)
or fit a new pool into a space designed for a different size pool?
Pics would help.