Can front small floorboard be moved back to give a couple extra inches legroom?

Half way thru annual now, I will see about getting a photo of it for you on Monday or Tuesday.

Interesting! When you eventually get around to having the whole thing opened up, is love to see a photo.

Found out yesterday the brake master cylinder is up above the feet on the firewall and is not the one in the parts manual. So this means I'll have to keep the hand brake on the panel and wait and order the brake pedal cylinder.

The foot pedal, which directly applies pressure to the master cylinder attached to it... plus a parking brake on the instrument panel.

The parking brake handle pulls a cable that's routed back to a pulley at the top of the firewall. that top pulley turns the cable 90º down to the floor where another pulley turns it 180º up. The cable then immediately terminates at the middle of the brake pedal lever. So... when you pull the parking brake handle, you're pulling the brake pedal down and applying the brakes. 
 

Sorry for the rough sketch. Not shown in the above sketch:

1. The cable is jacketed coming out of the pull handle. There is a bracket attached to the firewall that makes a 90º bend to the left and then the jacket ends. The bare cable goes over the top pulley (unlike my sketch the top pulley is actually parallel to the firewall) 

2. Between the top and bottom pulleys, a turnbuckle is spliced in to adjust the parking brake cable length.

3. The brake fluid reservoir is on the engine side of the firewall, immediately forward of and a few inches above the master cylinder.

My parking brake works very well. A modest pull on the cable is enough to absolutely prevent pushing the plane back from the fuel pump. Ask me how I know! I have the new gold-colored master cylinder from Alpha Aviation which is very effective - my old master cylinder was leaking when I purchased the plane so I have no experience with the older style beyond removing it.

I will have to investigate first, see what's on the other side of the floor board. Right now just have the hand brake, I do not recall seeing any remnants of a foot pedal. though if I am going to go full restoration to as original as possible, what did the original 415-C's have? Just a foot pedal or both foot and panel T handle?

Mac,

When you remove the rudder pedal kit... will you reinstall the brake pedal?

If so, the small "upright" floorboard is involved with brake pedal support bracket. There are a couple triangular metal pieces that are screwed to both the flat floorboard and the upright floorboard, and then a bolt going through them to act as the brake pedal pivot in between the two metal triangles.

So with the brake pedal installed that floorboard location is set in stone. Without the brake pedal... I can't see that it's doing anything else important except keeping my toes from jabbing the parking brake assembly behind my brake pedal.

That floorboard is pretty light so I can't imagine it would have much effect on W/B.