LSL7 work perfectly in DOSBox. The collections were very poorly done with what seems to be arbitrary decisions by people that know very little about AGI or SCI games or even DOSBox. The games used in the collections comes from a hodgepodge of sources. KQ6 came from the 2nd collection while KQ7 came from the 2nd stand alone version, which came with no DOS interpreter, so no DOSBox. This makes the game uncompletable on modern machines (firecracker speed bug) In the end there was no reason for the collections to have been done so poorly.
I have created patches for all four collections that allow the games to be run with the latest version of DOSBox and fixes a number of issues that many were having with the games. The King’s Quest collection also upgrades KQ7 to version 2, which can be run in DOSBox. Links to these patches can be found on VU’s message board.