reduce dev time for low intensity RLF

...my camera exposure was about 8 sec on FP4. The negs have come out rather contrasty looking (as expected). Development was 8 mins in FX 39 1+9. What percentage of time do you think I should shorten by?

I generally cut back or increase by something like 30-40% and also adjust exposure. Then again, I'm not inclined towards a subtle approach. I'd rather over compensate in order to get a feel for the dynamics and then home in on the desired end point instead of inching my way towards it. If you want to do the latter, consider an adjustment like 15-20%.