Non Removable Presta Extension Just got a pair of tubular Vittoria Rally road tyres. They look perfect but the problem is that the valve is 42mm which is no good for my new awesome 50mm rims. Above all the valve core is not removable so the extenders I've got with them are useless.

The question is if there's any mean to extend the valves up to 60-80mm in this situation or should I return it back to the shop?

Thank you in advance for your advised.
There are multiple types of valve extension:

The extenders you have relocate the valve core.

The other kind are a plain tube which tapers with a similar profile to a normal valve, and screws onto the valve, over the existing valve core. Once the tyre is inflated you can remove the extension and tighten the valve-lock-nut.