I have mixed and matched between Ultra and Mono A number of times without any problems. Mono uses more heat so ultra irons over mono very well but ammonia does actavate the glue/pigment of the mono for trim. When it dries I go over the edges with my trim iron and that really holds it down. About 95% of the time I only use Ultra for my own planes, I really don't like Mono even A little but I do use it for trim sometimes. That being said I have to say that Ultra Silver sucks!! I don't know why?? Mono silvers just work better??? See, I'm open minded but not to the point my braines dribble out. Not too much anyway!