[PSUBS-MAILIST] MK101 oil compensation tap

[Jon Wallace via Personal_Submersibles]

At first glance the MK-101 shell looks pretty thin.  I know they've been 
drilled and tapped to accomplish oil compensation but before I start I 
just want to know of any tips/tricks I should be aware of. Also, any 
reason nobody has drilled and tapped at the apex of the head on the end 
opposite the propeller?  Most every one has drilled in the cylinder body.

Jon