If you do wish to mount all scopes at once you may consider mounting the guidscope under the C8 like shown towards the bottom of this thread:
http://www.iceinspace.com.au/forum/s...ad.php?t=64805
This won't solve flexure issues but it shouldn't add to them.
You don't actually say if you have flexure issues at the moment. If you don't have any issues then I'd be saving the $500.
Let us know how you get on