ORIGINAL: r2champion
If I am understanding your question correctly, use a sheet of paper or cardboard to make an exact copy of you firewall....dimensions and shape. Once you have accurately cut the template from the paper, lay it on the firewall and copy your crosshair lines, or measure them and draw them on the paper. Mark your mounting holes from the motor to the paper. Accurately tape the template with the mounting hole marks onto the firewall and drill your holes. Am I interpreting your question correctly?
Not quite. Have a look at this - #37
http://www.rcgroups.com/forums/showt...=773195&pp=100
See what he made ?
I can draw around the standoffs but how did he work out the exact centres of the 'holes' ? Once you have them it looks easy to draw the lines which will end up mating with the ones on the firewall.