Lets see, two burning boxes outputting 96 hu/t to boilers accepting 96 hu/t outputting 192 steam/t. I’m sure this part is all fine as I can measure 192 steam/t in a pipe.
the pipe shifts 450 steam/t with a limit of 900 steam but theoretically should never reach that limit.
I’m expecting 384 steam/t but I think I measured more last night?
the pipes are set in series to one another with boilers under both and one end connected to the steam engine.
Going over 384 steam/t would cause the issue I was having of the engine overloading and making that awful thukthukthuk noise, 
should I be expecting more than 384 steam/t at any point? I’ll need to make some more measurements later to be sure.