I don't want to cause a fuss (OK, yes I do... ), but it appears there is a conflict between the IBRA rules on masts.
B.7.2 - Carbon mast sections may be used. (in Production: "NO").
B.7.3 - Masts must be assembled in the order specified in the normal
assembly instructions ("YES" for both classes).
From the 5.5 Sail page at http://www.blokart.com/product.php:
So, is it required (B.7.3) to use carbon lower mast sections with the 5.5m^2 sail or is it prohibited (B.7.2)?
Do not use fiber glass lower three mast sections.
The Ultra Carbon set (two lower mast sections) have been designed for the 5.5m sail. Use this with a carbon 3rd section and then three normal fibreglass mast sections above, which should be the minimum used with this large sail.