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Maybe with internal and external formers, which I assume is used for steerer tubes? Sounds complicated.
If you don't mind the extra weight, form the inside then mould the outside using way too much resin. Applying pressure evenly might be tricky since the interior will already be rigid.
Emyr-
There are various ways to ensure a good finish on both the A&B surface, internal and external formers is one but you can also achieve a pretty good finish by putting the part on a single sided tool and vacuum bagging it
I have an SBD crabon airbox on my jenveys and the inside surface isn't as good as the outside by any means, i don't think surface finish on the inside of the airbox is really that important as it's going through a set of trumpets anyway normally
mcmyk
What about the gram tho?