Dave,
I am 1853mm [6' 1"] and 86kg [190 pounds] so a similar size to you. I had a little trouble fitting thru Frame #3 of my Sea Cruiser with 32" x 16" Cockpit [still under construction] but overcame the problem thanks to a suggestion from Tom Y to curve the top edge of the 'masik' frame at the front of the cockpit not use the straight line or inverted V shape.
The top curve is still drawn thru the original Offset points and I made the curve of the cut-out in the frame 30mm radially below the top curve. This left 22mm of ply frame at the deck-beam notches BUT I put a western red cedar "doubler" on the fore side of Frame #3 to, firstly, save my shins from getting skinned and, secondly, to compensate for the slightly less than recommended 1" = 25mm of frame at the cut-outs.
This modification added about 35mm more clearance for my shins clearance . I have some pics if you send me an email

You may be able to adopt this solution on your Nikumi See yostwerks.com/SeaRiderMasik1.html

Cheers and happy building from Martin Bunny
Mandurah Western Australia
mcbunny09@gmail.com