I have f1 mirrors, i used some 3mm alluminium, Made the template from the old base plates. Mine are solid aswell. Aslo the rubber seal from the old mirrors i put that under the alluminium.
I paid £180 for mine.
2 Recaro bucket seats with rails
Recaro back bench
Recaro door cards and trd carbon window swich surround.
Got offered £700 for mine other day.
Think i got a good deal in the end.