What material for pre-seat insert....insert.Super hard foam?

[wioifoiee]

bought a 70 litre bead insert kit.
unfortunately i'm petite and a radical seat is quite large.

i need to find some material i can use that's ultra stiff, that i can carve into shape and place at the base and back of the seat first, before then creating my bead mould around me.
i guess something like packing material, or ultra high density foam that completely keeps its shape under a 60kg weight.

i've been googling 'high density foam' etc but difficult to find specifics on the foam in your regular internet shop and i don't know what keyword to use
Can anyone recommend anything?

like the below. EDIT: Think i've answered my own question...polystyrene foam is what i need

Edited by wioifoiee on Sunday 6th March 00:15

[HustleRussell]

I think Polyurethane foam is what you need, either in sheet form or in 2-part liquid. It is similarly light to polystyrene but is stronger in compression, more resistant to water and can be more easily shaped.

The liquid is the stuff commonly used to make race seats from.

[stevieturbo]

Why not buy a pour in foam kit for seat moulding ?

[ReverendCounter]

Plastazote foam is dense, light and cuts easily if you want something off the shelf.

[Boggo]

Just get a bigger bead seat kit - they are designed for exactly that. I have a fairly big ones in my caterham as I'm quite small (probably 4 inches+ behind my back to the firewall). Much better than using another material