I have to fir (spelling?) my shower wall out 1/4" to ensure the backerboard & tile overhang the showerpan flanges. I plan on ripping 1/4" plywood to do so.

Do any of you have any recommendations for how to secure the fir strips to the 2x4 framing? I think Framing nails or deck screws would be overkill - and block the ideal place to secure the backerboard to the wall.

Thanks in advance for the advice!