I'm not sure which one of you "building sages" recommended unibits awhile
back, but they sure are great for cutting transition holes/openings.  They
cut through the spar like the proverbial "hot knife through butter"!  Simply
outline/draw the pattern for the opening on the spar, "Swiss Cheese" it with
the appropriately sized unibit, "connect the dots" with a cut-off wheel,
finish shaping with Perma-grit tools, and then lightly sand the opening
edges with fine sand paper.  Presto - "factory perfect" holes !!!

Most of the building gurus already know all this, but I thought it worth
mentioning again for beginners or those new to LML.  FYI, you can likely
find a 3-pack of different size unibits at Home Depot or Lowe's ...

Dana Westphal
L2K-165
"Building over Geologic Time"