Advice - Seeland high seat extension?

[palmer_mike]

I'm soon going to be in possession of a Seeland Hercules fold up high seat. I like the idea of the extension that fits the Bushwear seat - does anyone know if one of these would fit the Seeland seat?

I've been told seeland dont make an extension themselves as they say an extension would weaken the structure, I am however not that big so not that worried about the seat collapsing on me.

Thanks for your help,
Mike