This topic was running in a different thread last week. IIRC, the conversion is setting up multiple container tanks for faster loading and selected drop. i.e. you might have some with retardant and some with water and can release part load on each pass.
The conversion also plans to keep the a/c within it's original design parameters. This means dropping at a higher altitude (obviously not as high as in the test) and so the tanks are pressurised to make the drop more focused and this appears to be the case with the test shown in the movie. You can see a jet directing downwards.
They hope that the capacity of the a/c, dropping sequentially in two (or more) passes, will offset the limiting factors of loading. But I sit to be corrected on all of the above.
Why do this? Hey, what else are they gonna do with all those '47s when the 380 takes over ...
