As long as you make sure that the W8 SSD is at the top of the boot priority in the BIOS, it shouldn't cause any problem.
What W8 glitch are you experiencing ?
If you mean that switching from W8 to W7 causes the PC to cold reboot, that's a consequence of the W8 "fast boot".
W8 doesn't really shut down or boot when you tell it to.
It enters a secret hibernation state and then resumes. That's how it manages to pretend it's booting really quickly, by not booting at all.
If you call its bluff by telling the W8 (pretend) "boot" that you want W7 instead, it has to really shut down W8 and then really boot again so that the hibernation state can be closed and a cold start of W7 commenced.
W8 fast boot doesn't work very well in a dual-boot, and can cause problems which cause chkdsk to be invoked when you switch between OSs because the secret hibernation leaves partitions marked "in use". That in turn can cause a hard reboot to assume that an improper shutdown occurred which it then proceeds to attempt to repair, taking quite a long time.
It's probably better to turn off the W8 fast boot unless you almost never use W7.
Go into Power options, select the "what to do when the power button is pressed", then the option to show the hidden extras, then untick "fast boot"