Non Taut dope is a must... Even with carbon veil, which shrinks less than Silkspan, balsa isnt that strong without is. The issues are that with regual taut dope and silkspan is can " suck in " or warp the wood underneath. I have used moulded balsa shells for along time, and have used normal Taut dope to seal everything. Its IMPOSSIBLE.. read - IMPOSSIBLE, not to get some element of Suckdown over a shell. I have ( in the past ) resorted to laying down carbon fiber inside the shell, with more balsa doublers for a top block, yet still have the suckdown effect. - Which to fix results in more filler, more carbon, more work, more WEIGHT.
I finally gave up a few planes ago and went to Non - taut and carbon veil and the ship stays the way I finish it in wood, no suckdown no dips or gaps. No more fill.
I will even use a 50 / 50 mix of non-taut over the open bay to lay it down, - Starting with just putting it around the edges 1st, let it dry, then lay it over the bay - let that dry then put full strength over that - with no ill effects, no warping. If doing a fin for example, I would lay .02 carbon veil over that to aid in the finish and strength.
Any other way ( IMOH ) is a waste of time.