I'm new to the GS, stupid questions.

If you use the regular 3,5" drive you need DS/DD 3,5" Disks ( double Side , double Density ) do not use HD ( high density ) they don´t work..... HD Disks have 2 holes ( one for write protection - one as mark to HD ) DS/DD have only one hole ( the read/write protect ) - it´s useless to close the hole and try to run HD as DD - it won´t work...
you can use the images without drive - but only in an emulation programm.... access is also possible in some conversion programms but only for conversion not for running...

Which 3.5 blanks should I be buying?

Oh, and is there a way to run disk images with ADT without using any floppies

Brad,

The only way to run the 3.5" HD Disks on the IIgs is with the Apple External 3.5" Super Drive. For that you need either the ASCO 3.5" Controller Card, or the special Apple Super Drive Contoller Card. ASCO Cards are not that hard to come by, but the External 3.5" Super Drive and Apple Super Drive Contoller Card are getting VERY hard to find and may cost you an arm, a leg, and your first born child. lol

I just happen to have a set on my shelf, but they are for a future project and I don't plan on selling them. Since I don't have any kids, I had to give up something of equal importance, but since I had two of the items in question, I could afford to give one up at the time. lol

You can also run the 3.5 HD disks with a 21meg floptical drive. It would do the 3.5 HD floppies and 3.5 21meg optical disks. But you needed a HD with the SCSI.

As running the disk images, the latess CFFA 3000 card looks like would run them loaded off a thumb flash drive in a IIgs. This run is sold out. I will be picking up one in the run of these.

Take Care