i do agree about the "top" as it is a gyroscope which makes the wheel want to lean if you try to turn it.... which is how a 2 wheeler "handles / turns" but i dont think this i a BIG factor here.
i find 1.5 - 2.5 inches of trail works very well...
my v max trike had a stock front end took 3 men and a boy to turn it ... about an hr or so an i wanted to stop....... and yes i know what your back roads are like
i made a set of trees got the trail down to about 2 .... i can ride around all day and not be sore at all....in fact 900 or 1000 miles in a weekend is not uncommon for me..... a friend had a servicar raked frame trike, rolling just down a hill i most ran into the building cuz i wasnt strong enough to turn it, probably 8 inches of trail.... i cut the frame so the rake was close to stock an made a set of trees,,,, go riding around w one hand was easy.>
if i understand you right your steering is easier with 2-3/4 trail than 2-1/2
i am thinking you may have had a bit more than 2.5 with the hard pull and wobble.... i find most of the wobble goes away when the trail is low.... long as the rear wheels are balanced an the neck bearing are not ready to fall out.. and it seams odd that there would be a big a difference in a 1/4 inch... just for chuckles do you have a hollow stem or is it solid??