Try this and watch what happens:
Marinate roast several hours.
Remove roast from pan/marinade, and place in smoker. (save the marinade)
Smoke for 90 minutes @ 250.
Place roast back in pan with leftover marinade and add 1 can of beef broth.
Cover with foil and continue cooking 3 more hours @ 350.
Tear it apart, mix with the au'jus.
Also, consider sirloin tip roasts instead. ;)
Lang 100 Deluxe trailer rig (60" smoker w/warming box and 40" chargrill)