I think there might be an easier solution for you. If you have a SCSI Zip drive, and a newer mac its a pretty painless process.

Here is what I did:

1. Format a Zip Disk (I formatted under OS9.2.2 on a G3)

2. Download and install the "Wish I Were..." Control Panel, set Gestalt ID to MacPlus.

3. Put in your floppy, fire up the installer, tell it you want to install onto the zip disc.

4. After it's all installed, hook the zip drive up to your plus, boot, and Voila! os 7.1/7.5 or whatever, on your Plus.

This process also makes installing web downloads and other software very quick, just load the disc in another machine and install.