There is a bug fix in the beta release today:
"Today’s Mini vMac 3.5.2 beta may fix a bug found by Tara Keeling in the Macintosh II emulation, where if the emulation was running slow enough (such as 1x speed), and there is a “disk1.disk” and “disk2.disk”, then the second disk image won’t get mounted. There is code to delay mounting the second disk one second after the first disk, which is good enough for Macintosh Plus emulation, but apparently not for the Macintosh II. So I’ve increased the delay to four seconds, but also now when a kDriveStatus call is made to the replacement disk driver, the delay is reduced (to about a fifteenth second). The emulated computer appears to be ready for a new disk after this call. (Not reducing the delay to zero is just being conservative.)
So even for the default Macintosh Plus emulation, when inserting multiple disks there is now usually much less delay."
http://www.gryphel.com/index.html#news
Mini vMac 3.5.2 Beta (April 16)
Moderators: Cat_7, Ronald P. Regensburg