I recently added a medium to my family. It compliments our large as NOLA said above. Check out the Woo 2 from the Ceramic Grill Store and the Grill Extender (group buy on this forum last month). These are two great eggcessories for the medium!
The medium is much easier to transport. We seem to be taking it all over the place.
I do tri-tips ofter! One of the family favorites! I sear for about 3 min each side at 700, then cook indirect at 375 degrees - 400 degrees til I hit 130 internal temp. SWMBO and the teenage girl like it more medium than medium rare.
I use a seasoning called Spade L Ranch. I've tried may other rubs and marinades, but I always go back to Spade L for tri-tip. Spade L Ranch is available here in So Cal at various supermarkets next to the meat counter.
I know I need to try the reverse sear method one of these days, but it's hard to deviate from something that's worked well for me in the past! Maybe this weekend...