LB1120 MIMO Antenna Question

I've been setting my friends (who live in a rural area without reliable internet) up with home internet using the LB1120 and some Wilson Yagi Antennas. I've been setting them up with one Yagi to start, and adding a second down the road if they need more kick (MIMO setup). 

My question is this: When I'm running the second antenna, do I need to run a second length of cable? Or could I use a pigtail to plug both antennas in to the already-ran section of LMR400 and then pigtail it again at the modem to utilize both TS9 antenna ports?

And if that works, do I even need to pigtail it at the modem, or could both antennas just feed through the same cable to one TS9 port?

Thanks in advance!