birdzeyeSince you wish to stay with the minitimer there isn't a problem. But since it only handles 8 unit codes and the TM751 will handle 16, your wasting usuable house codes!
Just remember to set them to different house codes!
I have to agree with
Dan Lawrence look more into Active Home Pro.
AHP will still work with your mini timer and you shouldn't need the TM751!
And it will be cheaper in the long run to go with AHP as X10 continually has deals on this with all plug-in included!