I have disabled this in LazY Puppy. I can run every sfs file i want as "substitute"-zdrv.sfs - even if it was new created and named WhereTheHellAreMyPasswordsICouldNotFindMySlippersAndSoIGetDrunk.sfsHowever, the puppy cloner will not respect one's choice of zdrv-xxx.sfs. It will ask you if you want to create a zdrv, and if you answer yes, it will create its own (6-7 Mgs), not the substitute main file you provided initially. This needs further investigation and testing.
Lazy Puppy can boot with every sfs file as "substitute"-zdrv.sfs i want to boot with.