Don't know if this will work for you, but I'm usually just careful about positioning of the mics and don't use baffles. I usually will place a fig-8 mic in such a way that the rear lobe is just capturing ambient information (ie pointing up towards the ceiling). When this is done, the natural null around the microphone is great for isolation from instruments that are close to the microphone.
In situations (such as a harp) where it is difficult to do this, I may place a standard studio gobo near the instrument to isolate the entire thing a bit- not just the mic. Either that or I use a directional ribbon such as a Beyer 160 where it isn't an issue.
That is good advice and what we usually do.
occationally we get engineers through that like to baffle (particularly the trumpet rca 44/coles 4038) and I figure it would be a good thing to have a few tools ready for the one time I have to baffle.
I would also like to experiment with a drier sound from the spots.
I quite liked the pics of Steve remotes "virtual baffle". Simple easy and probably quite effective.
I might make sure I always have a few of those ready just in case.
I use something similar when micing upright on location jazz stuff. Otherwise one gets a ride cymbal spot mic.
For the ribbon-- the guys at Royer cautioned against a rear lobe baffle because of the proximity side effects. I have not tried anything on the SF12, but using only one channel and being conscious of the side null is quite useful.
I am a little concerned about the oval shape as I imagine it would focus reflections back at the mic.
I would rather have something that is of a hemispheric shape even though it would isolate less.
The baffle does look interesting for certain uses though and it might well be worth checking out.
I've done something similar to what Yannick did with my SF-24 in rooms that were too live. For a session, I'll set the group facing a curtain with the mic's rear lobes facing into the curtain to minimize reflections.