I do it differently than that. I don't have to remove the filter. You retain the silver (SVT) or black (all other focus) faceplate without modification.
I send new HVAC back plates with the LEDs and wiring to make everything all plug-and-play. I make an array or LEDs behind the panels.
Daily: Audi S4 b5 | Project: Turbo ZX3
LED Conversions | Vinyl Carbon Wrapping | Powdercoated Valve Covers