What is the purpose?
For visual, what you are doing will work fine.
For imaging, how are you going to set things up? Using the refractor and SCT as main scope and guide scope, or vice-versa, will be flexure city. The only way to beat flexure, if you are imaging through the SCT, is with an OAG. You may have better luck imaging with the refractor and a guide scope, if the guide scope is light weight and mounted to the refractor's focuser (not the tube and not the rings). An OAG would work for the refractor, too.
For some good information about guiding with a finder scope, check out this link. Look at the 10 x 60 "Vario-Finder with Quick Release Guider Bracket Kit (1060VGKIT)" and read the description of the product. Even if you don't purchase it, it's got some excellent wisdom about flexure and the best way to mount guide scopes.
I hope that this helps,