U-Bass string tension

[Simon Neville]

I am a newbie, building a u-bass using baritone plans and modifications based on a Kala example.

Can anyone tell me how the string tension of the u-bass rubber strings (sourced from Kala) compares to normal baritone tension? I plan to use a carbon fiber rod rather than a truss rod (which the Kala has), but should I thicken the neck to help? Have looked online but can't find any references to string tensions of the rubber stings. ("Road Toad" strings).

thanks for your help!