I don't believe what I have just read. Calculating engine thrust is just that, a calculation. It depends on all parameters being ideal in order to get close to a believeable number. If you're trying to calculate the quantity of water a cone shaped beaker will hold, forget all the bullsh*t formulas and just pour it full of water and then pour that into a graduated beaker. Don't make something impossibly difficult that is excruciatingly simple.

Start the danged engine, hook the plane to a $20.00 digital scale that you purchased from Wal Mart, which is anchored to something immovable, rev the engine, let it stabilize, read the scale. If you don't get the thrust you want, change the engine out to a larger one until you arrive at the magic numbers you desire. I'm sure there are many guys out there who would let you borrow an engine to test your thrust with.