Yes, I'm gong to make my own!! I can do the L-shaped one and the centering ruler, too. I can get the very thin flexible plastic rulers (very inexpensive from my dealer) with the "zero" center mark which comes in 12". I'll just get 2 and cut them down to fit for the centering ruler.
On the L shape I'll get some acrylic and the guy I do accounting for has a shop where they have tools to set meters and such and he probably has just the right tools to make a L-shaped ruler!!
We all are GOOD...when we're not having brain dead moments! I'll let everyone know how it all works out.