Consierations
I would play slight draw with a touch of OE. Not enough to cause noticeable acceleration off the rails, just enough to avoid the dreaded undercut throw that can occur on soft center shots.
Another reason I'd avoid any soft IE on this shot, is that it may swerve the CB toward further undercutting, especially considering the cue will have some elevation over the rail if one attempts soft draw with touch IE.
The tangent line, for sliding CB is pretty good already, so I'd only want a touch of back spinning draw on impact.
I don't think the 9 comes into the shot unless it just misses the jaw and has significant OE on it.. even then, it may help to hold position.
Anywhere between A and B on my diagram below would be nice shape.
Just my opinion!
Colin