Most concentric pots seem to have ~1/4" thread length, which is really only useful on pickguards and control plates.
I think the longest ones I've found are the Alps Stacked Dual Concentric pots (250K, 500K), with a threaded section length of 8.75mm... still pretty tight but maybe just doable. NOTE: The Alps style pots require different stacked knobs than the CTS stacked pots, so check before you buy.
I've got a couple out in the shed, so if you can wait until tomorrow I'll double-check the thread length for you.
Edit: These look to be the same pots on Allparts, but they list them as 9.5mm thread (250K-250K Concentric Pot with Detent, 500K-500K Stacked Concentric Pot).