I drilled my angled passages out (dont remember what to, it was what Sanborn posted) & just CAREFULLY went in the OE holes very slowly with a variable speed drill/bit/no jig & had a helper feed lube on the bit being very carefull not to even go a hair sideways as their big caveat (when I read the procedure being tried by someone that posted) was that if the bit breaks off in there it likely is a trashed block. thank you for the heads up on the thick/thin "sides" on the center (3) bulkheads & the "jig". Sharpen the bit on a drill doctor before doing each hole.