Yeh well done.
Lots of great info in that link as stated above.
Go to page two in this link below and it will certainly sort things out for you. It's using an old section of fibreglass mast.
I originally used straightened out windsurfer booms with a wooden plug in the end to take the plastic "rowlock". Over time I proved they weren't up to the task with sails over 5.5m2 though.
www.seabreeze.com.au/forums/Land-Yacht-Sailing/Construction/Build-a-Landyacht-Lake-Lefroy-Mini-Yacht/ Catch you in the land sailing section.
Chook