Heath H-89 & Magnolia Disk Controller

I'm trying to get a Magnolia floppy controller running in an H89, and I'm having some odd problems. The Magnolia controller apparently requires their own monitor ROM, which I have (444-84B revision 10). It's my understanding that this ROM actually negotiates the baud rate with the terminal logic board rather than requiring a fixed 9600 as the Heath ROMs do. However, when I have this ROM installed, the machine doesn't seem to be able to "sync". The CPU and TLB speak together perfectly with the normal Heath ROM (444-84 or 444-142), so I'm inclined to rule out problems with the UARTs, transceivers, and cables. But most of the time the screen spouts gibberish with the Magnolia ROM in place, and when it does sync up, I can't type more than a few characters before things go to pot. I've also gotten the same behavior with two known-good CPU boards. Any suggestions? Does anyone know if revision 10 is a good version of Magnolia's ROM, or do I have it because the guy I got it from uses version 11 in his '89? :-) This controller supports a variety of 5-1/4" formats, as well as 8" drives, so I'd love to get it running. Thanks! Patrick P.S. Yes, I do have the "other" recommended Magnolia PROMs in place... full set is 444-83 (Heath), 444-61 (Heath) and 444-66B (Magnolia). --P