Hi to all

I just signed up ... been reading a heap of post on here and it has inspired me to build a land yacht...it's been really good and awesome to see how supportive everyone is ....
So I would like to build a 2 seater .
Any thoughts on the steel I should get ( round or square) .
How heavy I should go with the steel?
How heavily should I brace the mast mount?
Iam thinking about a 6m sail as I have 2 old windsurfing but all my sails have been rat eating

.
I think the mast are about 4.5 m long.
I have sat down and scratched out a bit of a start plan but not sure if I should go with it
Any help or ideas would be much appreciated