Sounds like a plan to me. Baby backs cook differently from St. Louis style spare ribs. After 2 hours, check for donenes with the bend test, and adjust your times from there. Some will take a little longer, some will be nearly done after 2 hours. But 2 hrs at 225 will probably require more time. I cook mine at 275 or there about, and after 2 hours, I can pretty much judge how much more time is required. They are done when they bend freely without breaking apart and the meat is tender when probing between the ribs with a tooth pick. Good luck, and what time is dinner going to be ready?
UDS, cheap o grill, rusted chimney, yeller wannabe thermo pen, Maverick ET 732, 1950 model wife.