Like, I said, no problem with 245/40/17 on mine. The 225/45/17 will be fine as well. My stock tire size is 225/50/16. For comparing tire circumference, I like to use this tool: http://miata.net/garage/tirecalc.html
Being out by 1% or so is no big deal, stick to that and you won't have any odometer anomalies. The ABS and DTC should be similarily unaffected so long as you keep the circumference the same. The larger your wheels, the higher the unsprung weight, so braking may be a concern ... especially if you're looking at 19" or 20" rims.