Water supply for basement bath

We're in the process of finishing a bathroom rough-in in the basement and about to tap in to the water supply lines. They're 3/4" (overhead) and run along the bottom of the floor joists of the first floor. To install a 'T' we're going to have to cut out about 1/2" chunk to make way for the 1/2" feed to the new valves. My concern is after cutting the supply, I'm not sure if we can separate the 3/4" line enough to slip the 'T' in place. What other options are there ?

tee

Slip coupling, union, three elbows with the tee to make an offset are some of the options.