I claim ZERO expertise.. My guess is that having a degree of toe-in reduces the inclination of a pair of wheels to wander at the slightest hint of influence, be that camber alteration or a uneven road surface. I would have by nature thought parallel might seem ideal to resist uneven tyre wear/scrubbing, but I find no such issues on my +8`s tyres that are noticeable to the naked eye with 1/8th toe-in... As to how much different it might be to have only one wheel following on behind, relative to the geometrical positioning of the two front wheels... I have no idea.. With your very Morganesque set up to hand, it seems a bit of trial and error may be no big deal..?
Good luck in your choices..
