As far as I know, it was only the very early Sprints that had the thicker front bar, may have been the original 2000 cars or thereabouts.
I have VA 2245 AND VA 10224 ( both series 1 cars) in my yard ATM so will measure them and compare them to the Carledo's bar which came from an '80 model Sprint (Series 4 car) and my own '78 series 3 Sprint's bar (VA 26140)
In the meantime, you could try removing the rear bar and see what effect it has, it's only a few minutes work after all and softening the rear has the same effect as stiffening the front, but costs nothing!
If you have adjustable shox, you could also try softening the rear settings a bit and see what that does. I know it goes against the grain to suggest SOFTENING the ride, but, as I found out, it's all about balance!
On tyre pressures, I have no opinion, not having had a stock Sprint on the road long enough to form one and there are too many variables anyway, make, compound, age, driving style, all affect the optimum, so this is something best sorted by experiment. FWIW, I reckon running the rears a tad softer than the fronts, suits me best......but that's me and is purely subjective!
I COULD regale you all at length about the trials and tribulations I had with getting the Carldeo's handling balance set right, but it would be pretty pointless, since the car has different overall weight, CofG, axle weights, spring rates, shock settings etc et boring cetera to a conventional Sprint powered 4 door, so any data i've gathered and settings i've used are not really relevant to anyone elses car!
2 door '73 Toledo with Vauxhall Carlton 2.0 8v engine OWF 797M (The Carledo)
'78 Sprint Auto with Vauxhall Omega 2.2 16v engine EGP 247T (The Dolomega)
'91 Cavalier 2ltr 8v auto
'95 Cavalier 2ltr 16v auto
Spectrum Auto Services, Servicing, Repairs, MOT prep. Apprentice served Triumph Specialist for 45 years and home of Maverick Triumph.PM for more info or quotes.