If you need tag axle for driving straight, you start from wrong point.
Tag axles are for extra weight carrying and on good coaches they are liftable.
I had my vintage Prevost park in spot with sharp turn required, so lifted tag for better turning.
200 miles later I start thinking "did I lower the tag down?"
I did not and could not tell the difference in driving but fact is that it was slower driving in weekend traffic.
The tires on bus conversion operate at 60-70% of weight carrying capacity, so dropping another 30% is not posing any danger.
Beware about designs where builder overbuild the coach on small chassis and add tag as bandage to cover inadequate design