Trust me on this, if you can blend, even a little bit, it will look so much better. With even the slightest overlap of two butted edges, your intensity increases and it is very noticeable.
Something of a concern, you mention 120'. That would mean a single projected image size of 30'x40'.
I am not sure what projectors you are using but that is a huge image.
I typically use LX-100 10k projectors and the largest size I would ever shoot is 18'x24' and that is in low light. Even if you are using a 20k projector, 30x40 is still huge and will only be about a tenth as bright as a typical screen.
If you're worried about running everything off of a single Catalyst, remember you can use 2 TH2Gs and run 5 projectors and put your HUD on one of the six outputs.
I have some intensity equations if you're interested.