Heavy favorites are attractive when you focus on the run line. Betting on the run line can be a bit tricky though. One trap : a winning team playing at home wouldn't need to play the 9th inning if they are winning the game and therefore shortening the number of innings played.
I hit some nice streaks last year focusing on run lines. Once teams have played enough games to generate reliable data, I will test some strategies I used last year.
I'll mostly play runlines laying 1.5 runs with visiting teams.
Visitors look for insurance runs in the 8th and 9th. This option isn't available to the home team in the 9th inning.
Never forget how Boston covered for me last year on the RL against these Devil Rays. I was down in the 9th by 2 runs, bases became loaded, and you can guess what happened. TB was terrible late in games!