My guess is The Swarm's will be on the exit of the Zero-G roll, and possibly another on the exit of the inclined loop.
Thanks for clearing that up Adam. After asking about it, I did some research myself and after also being quite shocked at the scale of the plane, I figured that the "twisted metal" from the detached engine would act as a support for the wing, but well done on delving further and finding that quote from the section the majority of us would simply skip. It is very interesting that Merlin are constructing the plane to their own specifications as opposed to buying a cheap skeleton and wedging it in the ground. It's going to be one helluva tight fit through that gap between the engines. I did a bit of searching myself and I found this video about the construction and technical specifications of Raptor:
Forgive the Italian man, but there are subtitles and at 1:15 you can see that he specifies that Raptor's trains weigh 18,000kg, are 14 metres in length and 6.5 metres in width, so we can assume the same width (at least) for The Swarm. Looking at the same plans that Adam posted, we can see that the engines will be 3.1m in height and width, meaning that it will indeed be a very tight squeeze for the train. I did some ratio calculations, and worked out that the gap between the engines is 6.8m. Somewhere along my line of calculations I appear to have made a mistake because that surely wouldn't be allowed?