How can I play multidisc backups with only a modclip???

[spooky]

External mods are notorious for causing problems with backups either single or multi disk!

I would strongly recommed getting an internal mod installed.

As far as the disc wobble is concerned then all disks will wobble to a certain degree, obviously the missing bearings will make this alot worse and could create a situation where the laser cannot read the disc correctly causing the PSX to fail during booting or gameplay.

The PSX units anticipate a certain amount of wobble and internal settings help the laser compensate for this and in most cases it should track correctly, but i think that the amount of wobble you are getting due to the missing bearings will be too much for it to handle.

Sounds like a new laser is required!