I tested directly connecting the weBoost Drive 4GX booster to AT&T and Verizon JetPacks that have dual antenna inputs for MIMO. The results were outstanding! Links to parts below.
Amazon Links:
weBoost Drive 4GX: https://amzn.to/2NQGGWg
SMA Female to TS9 Splitter: https://amzn.to/2OlUOG6
SMA Male to Male Extension: https://amzn.to/2Ojs4Od
SMA Male to Female TConnector: https://amzn.to/2rLgDXL
SMA Female to TS9: https://amzn.to/2QlYsSM