JonM,
I have had very good experiences with Trac-Vac over the years. All vacuums work best when: (a) the grass is not too tall (don't try to cut off more than 2-3 inches), (b) the grass is dry (no rain or heavy dew on the leaves), and (c) you operate at a bit slower ground speed than when mowing without the vac. Be sure to run at full throttle or whatever is required to get a true 540 PTO speed.
You will find the trailer dumps better if you don't pack it tight with clippings. Knowing how full it really is requires some trial-and-error, but you will be time ahead if you don't try to fill every cubic inch of it.
Please post some photos after you get things running.
JackIL