I installed the front floor boards tonight. It’s pretty straight forward. The only thing I did in addition to what’s called for in the plans is I added some fireproof spray foam insulation. This should help for both heat and sound insulation in the floors, as well as give them a nice solid feel. The foam I’m using here is called Abesco Fire Rated Foam, FP200.
FUTURE EDIT (6/16/16): Having finished the plane, it came out a tad porky. I’m not sure I would have used as much foam in the floorboards as I did, if I were to do it again. At a minimum, I probably wouldn’t put the foam under the rear floorboards, to save some weight. It does give the floors a VERY nice solid feel, but if you’re concerned about weight, cut back on what I did here. Maybe only do the front half of the front floorboards with the foam. I used at least two cans (possibly more, memory gets fuzzy fast), and I’m sure it added a few pounds minimum.