Winds on approach

I flew yesterday and did some practice approaches, and the winds were
about 20 knots gusting to 26-28. I've flown almost all approaches so
far in a different 172 that had a 180hp conversion. Because of the
winds, I kept almost full cruising power on the descents to try and
maintain my normal 90 kts ground speed for timing and roughly 500fpm
for the ILS.

This plane did have an IFR GPS indicating ground speed, but the one
I've been using for all other approaches didn't, neither DME. The CFI
informed me I should have used known power settings. What are your
thoughts? I'm not sure how I would've known the right power setting,
unless I used what I normally do, and accept the lower ground speed,
then adjust my descent for the ILS to a much lower fpm descent?