Macs really don't have provisions for providing delays to adjust for devices that take their time to come online. But, there are a few things you can do to compensate:
First, you should check your drive connections. Since you're running 7.6 and 9.1, I assume you're using a pre-G3 Power Macintosh, most likely a 7000/8000/9000-series machine or comparable clone (because others often lack space for extra drives). If you're using SCSI, check the cables, IDs, termination, etc. Some drives have features that keep the drive from spinning up until it receives a command from the host, so if such a feature is suspected, you might try downloading the drive's data sheet for proper jumper configuration.
Second, you could try LaCie's SilverLining. It may provide the ability to pause the computer's startup until a given time. No guarantees on that, though, since it's been a while since I've used that program.
If SilverLining or some other disk utility doesn't work, you may want to increase the amount of RAM in your computer. Since your Mac will test all of its installed RAM during its POST, the POST will take longer with larger quantities of memory available. This will buy extra time for the drive to become ready.
There may be an OpenFirmware trick you could try. I'm no expert on that particular subject, so somebody else would have to jump in with that.
Failing that, you could move the OS to the slower drive, so the computer has no choice but to wait for that drive to become accessible.
As a last resort, you could do a soft reset (press the reset button or Command-Option-Power) before the OS starts to load.
That's all I can think of for now.
