thanks for the input
Thanks very much for your suggestions (and for the article). I'm actually an animal behaviorist, and realize that this will take time--my husband is the impatient one! We have a gate at the foot of the stairs, though Star is very strong and I suspect, if highly motivated, could push it down. The only interactions so far (except the inadvertent chase) have been when Star was crated, and she ignored Artie. Artie won't even come down now when she is crated, so he needs to relax more before we try this again. I'm working with Star on basic obedience training, and she is pretty good at sit and down. I'm working on stay, and also want to introduce "no" (or "drop it") before trying an intro again. Easy enough to have her on a leash for an intro, but I don't want to force Artie into it; it will need to be when he's ready! I've attached photos, too.