Hole location for Herbie for overflow's

[Palmer]

So I drilled three holes in the tank tonight with the 42 mm diamond saw and wouldnt you know the 1 " bulkheads DONT fit!! It goes right up to the external thread (about a half a cm in) and just stops doesnt seem like anyway to get it through. I wrote BRS an email but honestly all the 1 " bulkheads they sell have the external thread so now I dont know what my options are...

Anyone run into this before?

The hole is pretty clean there really isnt any significant jagged edges....

Palmer