You're absolutely right but even if we add another .3 or .4 for the coil to his measurements we only get about .7 which is still under the .8 mentioned in the manual. I would expect a very high static in a mobile home setup so the fact that his may not be that bad makes me wonder if the motor is set up correctly. I had a job where an oversized VS AH was installed & the duct system was designed for a 1.5 ton. The place sounded like a wind tunnel it was so noisey coming out of the registers. You thought they were gong to blow off the wall. It was an older model unit & there was no setting lower than 1050 cfm not even at continuous fan. Even two days with the distributor tech support rep & the manufacturer support rep we couldn't find a way to slow it down. I can't remember the tsp but it was so high we were laughing about it. I have no idea of the actual CFM it was moving but I guarantee it was a lot closer to 1050 than 600 even at ridiculously high static. If the OP's ductwork is too small & the motor is set up right it should be blowing his curtains off the walls. If the ductwork is blocked up somehow then his static pressure would go through the roof. Oh, we ended up changing the AH.
I don't think his air handler is rated to be able to deliver set CFM at statics above .3". Since its rated CFM is at .3", and it only uses a 3/4HP motor.