The clear aperture on the Celestron bino is about 20-21mm. The field stop on the 19mm Pan is 21mm. So the field stop should still have about 50% illumination -- slightly dimmed but not noticeable -- it should be fine. One thing I don't like on the 19mm Pans is that the eye relief is starting to get pretty tight.
I've started experimenting with a pair of Baader Morpheus 17.5mm eyepieces. These have about 20mm of eye relief. I like them so far, but it is still too early to report. If you search the binoviewer forum for various eyepiece names, you should be able to find some reviews.
The Nagler 13mm T6 are nice for binoviewing. Reasonable eye relief and very wide view. Thats probably my favorite in the 10mm to 15mm range. Much below that you are probably better off adding a Barlow lens.
Another idea would be to get some thread-on Barlow-like lens you can put on your bino. Just double the power that way, and the 35mm Ultrascopics become 17mm, etc. I've not tried it, but this Burgess screw-on 1.9x bino lens is $10. Seems worth a try. There are other similar products around...
Edited by ngc7319_20, 18 April 2019 - 08:11 AM.