Creating Skimboard need your opinion please!

Hi to all!

I am new at this and have been doing extensive research on skim/surfboards. I am setting up to build my own skim board and i have studied all of the different types of cores; polystyrene, polyurethene, and polyvinyl. Now it seems that most ppl are using polystyrene #2 lb density, for a common home made board. Exile, Zap, and Victoria all use polyurethene or polyvinyl for their cores.( mostly polyvinyl). And their cores are 5-8 lbs in density rating. So this seems like a HUGE difference in quality and durability correct?

 

 I am thinking of trying the polyvinyl route for creating my board. Now i have a question and please dont bash me, for i am new at this and researching.

1) what is the big difference in polyvinyl foam and a regular Polyvinyl 4x8 exterior sheet?

Does it weight much more?------- Is it too rigid?----bouyancy?

I really appreciate any input, opinions, or ideas

thanks,

gordon