The VPM tubes are less than 40ft deep, unless they stick out a lot farther from the hull. A Tomahawk is 21ft long, not counting the gas generator (I do not know where the gas generator is located in the VPMs). It's not clear how long CPS/LRHW/Dark Eagle are, but ~10m/33ft looks about right based on the picturess of the TEL trailer.
I'm not sure if the agreement that a non-strategic tube is one not deep enough to hold a Trident still matters, either. Remember, the VPMs are shortened Trident missile tubes with an insert holding 6 or 7 Tomahawks in a MAC or 3 CPS in an APM.