So I’ve gotten Tri Tip dialed in for my personal tastes. 135 F for 16 hrs. Bam ! Probably my favorite protein to eat.
But here’s the thing… Most of my Tri Tips have been around 3 lbs. I started one last night that is close to 5 lbs after trimming ! And I left a good amount of fat on it too. Who’s afraid of fat, right ? 
Anyway, at 50 or 60% heavier / thicker, would you maybe go 18 or 20 hours, even if 16 hrs was perfect for smaller hunks ? Or will it make much difference ?
For obtaining the same core temperature the time goes from 1hr at one inch to 3hr at 2 inches thick. What is unknown to me is the time relationship for a thicker cut and tenderness. A couple of extra hours might do it but I thinik it is a bit of trial and error. You may not be able to detect any texture difference but I am not sure.
Is it both about 50 % heavier and thicker?
Only the thickness matters.
Thickness makes all the difference because heat has further to travel as it diffuses into the meat.
I’d try it for 20 to 24 hours as it’s likely from a larger and more mature animal than your prior Trip-Tips.
Yea, its bigger in all respects. And more fat on it too, even though I trimmed it. I didn’t try to go too crazy. As a Keto’er, fat is not a bad thing
I’m leaning towards 18 - 20 hrs for this one. I did a smaller one for 20 hrs, and it was almost too much… Too fall apart tender.
Chris, fat is flavour, particularly after seasoning and searing.
Measure this TT’s thickness and record the details of the cook so you can repeat your success with this size again.
For this cook you are adding either 13% or 25% more time for 50% more meat.
Oh for sure, already recorded 
I have a note pad app on my phone. I
After about 50 or 60 SV cookings, I have most of meats / cuts I’d ever want to cook, dialed in with times and temps recorded.
Now I’m just starting to play around with different seasonings and marinades