I have a pdf of a dimensioned cad drawing I made of the front triangular motor mount. I will have to do some digging, but I can post the dimensioned drawing if you like. Print it on full sheet label paper (full scale) and stick it to your flat stock as a pattern.
I can't seem to find the drawing I made of this. If I don't find the drawing soon I'll measure up a bracket and draw a new one if you don't find one first.