Some very nice work you have done there Smokey, especially with the steering head and use of the bicycle stem and clamp. I did mine very similar to that and it does save a lot of fabrication by using "off the shelf" bike bits.
The seat set up looks good and comfortable too, but for performance a very much more reclined seating arrangement is recommended. Also from the photo it would appear you have very long legs. Unnatural even.
Use of stainless steel may seem to be a good idea from the point of view of rust etc, but for the components that will be subject to high stresses, it is not really the best choice as it does not have the "spring" qualities of carbon steel.
I have bent three stainless blokart chassis's under fairly normal usage while my steel blokart has remained straight under heavy usage.
No doubt the blokart people would dispute that but they are more sales people than they are metallurgists or engineers.
Was there something you did not like about the "Lake Lefroy Mini Explorer Design"???
It is very well proven, beats the pants off a blokart and comes from someone who has over thirty years of sailing, designing and building land yachts.
From personal experience I can tell you that if you build one of those it is a proven experiment and you will get the thrills you are looking for from it.
The plans for it are downloadable from this site for FREE.
Anyway, this appears to be your first yacht, so complete the experiment and keep us posted on the progress and results.
Once you get the complete thrill of sailing a land yacht, you might even want to flog the hog.

Welcome to our world. Cheers Cisco.