Over the years, I've seen a couple of guitars that had the body's heel rout split, apparently because the wood contracted with age. The holes were tight to the bolts, & the plate prevented the bolts from following along with the wood, & something finally gave. And I've seen another that got dropped, & the rectangle of wood between the four bolts tore out of the heel pocket, like 1/8" thick.
A plate is like the Model T's paint selection: "any color you want, so long as it's black." If you put a plate on, 99.99% of them offer you the "choice" of four holes & 2.0" by 2.5". If you're feeling especially radical, you could put on... wait for it... a
black rubber gasket, just like the ZZ Top song!! Oh, wait... :glasses9:
Two holes drilled on about the same piece of wood grain is NOT structurally smart; two screws sunk into the same line, no smarter. Yet we go ahead & do it twice on most bolt-neck guitars. The three-point Fender is the smartest move made in this direction, but I figure it never caught on because (per common wisdom) three screws isn't as solid as four.
I build transit buses for a living. If you don't believe that four bolts is waaay more than enough, considering that total tension on a six-string guitar is less than 100 lbs, you
really don't wanna know how many major bus components are held on with LESS hardware. :laughing7:
Now, if you're planning to whack the guitar against a brick wall on a regular basis, or throw it out the apartment window once in a while, then you might want to think about structural stability. Really, though, the tension on a "heavy-strung" electric is
nothing compared to any acoustic guitar.
With ferrules, it's simple: you can put in a whole handful (or more) & drill holes just about wherever. If there's a questionable spot on the heel of an otherwise lovely neck, you can readily drill 1-2 mm away. No problem to taper the heel or pare it back (like a small version of what Stephen Davies did for the early Washburn Nuño guitars) or even sculpt it. My Martinson bass (five-string fretless) has five ferrules, which is overkill but looks good; my Austin-cloned StingRay four has only three, yet has incredible sustain & no noted stability problems.
At least as important is that the neck-to-body fit be as tight as possible. If that joint is stable, & you're not loading it up with a .012 or bigger set of strings, two bolts would probably suffice (through the outer edge of the pocket, naturally).
But if you reduce pocket thickness, then PLEASE don't forget to use shorter bolts!! It's just depressing to see two little steel points poking up at fret 19....
If structural stability is an issue, consider installing steel inserts into the neck. (Better still: pull the fretboard & put the inserts on the far side. It's totally daft overkill, but that's how us mechanics think. :icon_biggrin
