After drilling the hole in the Left Elev Horn I made a block out of hardwood the thickness of the gap between the left & right horns. I used my dial calipers to and determined I needed a block about .940 thick.
My friend Jim calls me a cheater and maybe I am.....but I took the block out to my mill machine in my shop and machined it down to size....exactly .940. The block slid inbetween the horns very nicely. I located it to where I felt there would be plenty of meat around the hole in the wood. I marked the location of the hole in the Left Horn. Next I drilled a #12 hole through the block in the location I marked from the hole in the Left Horn.
I set the block in the horns, then clamped them with the wood inbetween very tight while using the #12 drill to locate the hole in the block in exact alignment. Then taking the drill and being certain I held it nice and perpendicular so it would l"leverage" the block out of position I carefully transferred the #12 hole through the Right Elev Horn. All worked well and MED's were ample. Pics below show how it came out in the end product.