Hiko,
The mast we had at Yeppoon was Paul's three piece ally mast. I think he did say that it had another section that could be added to it to accommodate a 5m sail.
I thought it was an excellent piece of work and that it's stiffness is a major reason why the yacht performed so well. Aluminium is readily available here, not so used windsurfer masts so I will opt to build an ally mast when Paul publishes the specs.
He took the trouble to point out a disadvantage of the ally masts. That is, due to the ally not being anodised, the combination of moisture and the abrasion of the mast sock on the mast results in a black and smeary residue on the mast which may stain your sail.
As to which is the better mast, ally or wind surf, you will have to ask the master. For gusty conditions or for the "trouble and strife" and the "billy lids", the wind surf mast may be the softer option.
My 11yo son Nic was quite happy sailing Diablo all day in 8-12 knot breezes but when the wind got up the next day and he saw how fast I was going, he said he would rather sail the blokart that day. Not fear I think but good judgement.
Thanks for the compliment. With the approval rating the yacht is getting I must have got most of it right. I am sure we are going to see more of these great little yachts around. I must say again though, most of the credit goes to Paul for a great design, his excellent build thread and drawings and his insistance that I "stick to the plan". For anyone considering building, I urge you to do the same. If it works, don't try to fix it.
Something I haven't mentioned before is that Paul bit the bullet at Yeppoon and offered "Nappy Rush" up for sale to save him the cost and me the trouble of shipping her back west. The price was good so I was not backward in coming forward.
Haven't had a sail in her yet but when I do I am sure it will be another dimension. This yacht is really compact when disassembled and I am sure at least two would fit in the boot of my Falcon. Cheers Cisco

P.S. Despite the two additions to the family, I am not about to sell my blokarts.