I have loads of Pauwlonia for sale - nicely dried and straight - 150cm x 10cm x 6mm thick - £9 a sheet or £80 for 10 sheets . (Plus postage)
I also have some 4mm left, but not much, The 6mm will easily plane down to 4mm in a decent thickness planer.
Also I have some 4 x 4 inch timbers (approx 6ft long, but I will measure asap) - enough to make a hollowed oldstyle shortboard
Pic attached of my last board made from this (the darker stuff is the pauwlonia)