i have a 30+ y/o gunite Pool with a Hayward SP583 light. Problem is that the OE chrome faceplate was chipping and we were told to replace it with the thermoplastic one. Now the lamp won’t stay in the niche, as this model was held in by wedges. I noticed the screw hole for the new faceplate was closer to the center of the lamp than the chrome and I wonder if this is the reason I can’t get a grip between the niche and light fixture. 

Parts:

light - Hayward SP-583SL

Wedges - Hayward 132 x 2

face - old: Hayward SP0583SL

face - current (doesn’t quite fit) Hayward SP0583L