The top ridge isn't worth the time it'd take to remove it.
Just call it the "Keystone Inverted Keel". It could actually
be considered a "design element".
The scoop hotwire sounds like the best approach for smoothing
the interior front - why immerse yourself in the foam crumbs/dust ?
You'd end up looking like the Pillsury Doughboy [encased all in white]
as all those foam beads would be sticking to you either from the
static electricity or heat induced rivers of sweat...
Cheers,
Norm/mezmo