If you guys look close at DB's model with radials you will see that the radials are out of phase with the top 1/2 wave radiator, plus radials typically show cancellation due to the apposing radials producing currents that are flowing in the opposite direction, thus radials contribute very little to no RF into the far field.
The Big Hair's 1/2 wave over a 1/4 wave idea is nothing more than another way of adding slanted down radials to the radiator, very similar to what DB's model shows us.
BH's collinear stacked 5/8 wave idea with the shorted phasing stub setup attached between the two radiators may have some gain/angle advantage in the design however, but I doubt seriously in the real world...it will make the 7.5db gain claimed.
Driving around in a mobile to test a base antenna is fraught with many additional variable issues that must be considered, however you can get more dependable results if the mobile is stationary, and testing just one base locations.
It is not possible to consider all the things that might get in between the antennas at any point when moving around in a mobile. Even the Earth effects with a low profile mobile antenna can vary considerably within a few feet, and with vehicles and other type obstructions in the way as one passes by...the task can become fruitless.
Like the old say goes..."if the idea or results seem too good to be true, then.........."
