I spent AGES looking and trying cheap solutions for my f2, including the 954 solution, f4 shock with the stiffest spring from all major companies I could find and every other suggestion i could find online. At the time i was probably 16stone without gear and none of the solutions worked.
The geometry and weight of the steel frame (plus my above average weight) meant every spring / set up was just too soft.

You could go for an F3 remote res shock and have it rebuilt for under £100.

I ended up going for an ohlins.