Paper exposure data for Ilford MGIV RC, FB and FB/WT is available on Darkroom Automation's support site. Although meant primarily for users or DA's f-Stop timer and Enlarging Meter, the data is applicable to all darkroom workers.

http://www.nolindan.com/da/support/index.htm

Graphs showing the print zone Vs exposure relationship clearly show the effect of each contrast filter.

http://www.nolindan.com/da/support/mgivrc-zone.jpg
http://www.nolindan.com/da/support/mgivfb-zone.jpg
http://www.nolindan.com/da/support/mgivfbwt-zone.jpg

Darkroom Automation now supplies footswitches for its timers at $29 each:
http://www.nolindan.com/da/index.htm