Just to say I haven't forgotten this thread. I have ordered a Lumicon #29 Dark Red filter (I think nominally 600nm Longpass) and an Astronomik Proplant 642 BP which passes between 642nm and 842nm. I plan to use these with my ASI 224 MC for EAA with galaxies. The #29 Dark Red should detect more alignment stars, while the 642 BP with 200nm width of band pass should yield less star bloat or chromatic aberration with my achromat Celestron 102 SLT, and when the moon is out in force. I have been struggling to decide which one to buy and eventually decided to buy both, to give me options for different objects and viewing conditions.
I think the H-Alpha filters have too narrow band pass and will require exposure times that are too long for my Alt-Az mount.
I will be very interested to see how much contrast improvement you get on galaxies using these two filters relative to no filter. I've read all of Jim's excellent articles and tests on filters, so it will be very interesting to learn of your results. In particular, I would be interested to see if the #29 needs roughly 6 times as long as a no-filter exposure to start to wash-out the sky background with the ASI224. I think Jim did his tests on M33 using a Mallincam Xtreme in part 4 of his series on Managing IR in video astronomy. Please let us know how it works out for you!