I'm not able to find this in the forum and not sure if is has ever been needed.
Is there a way to hide a product option drop menu with an if statement? X cart developed a mod for me and for the customer to be charged the right amount we need to make it a product option in the admin.
See
http://www.hoseinahurry.com/1-4-stainless-steel-braided-hose.html and see the option "Hose Assembly OAL Length". This is tide to the hose length for calculating the price of the hose when added to the cart.