Hey Richard,
I don't have time to test your mod but just looking at the HDV, it looks nice!
For the MNRL 1975 F1 mod, I added a few of the AMS upgrades but I did not include the new Advance Transmission as MNRL is an older gent leagueand the issue with that mod was tire temps.
So my two cents on the shift timing is:
As your UpshiftClutchTime=0.08 and your DownshiftClutchTime=0.20
The AdvancedUpshiftDelay should be similar and not 0.21.
The AdvancedDownshiftDelay is fine as it match the 0.20 of the clutch time.
The Sequential=0 is what makes the tranny go 1-N-2-N-3... and I'm all for it as I have shifted Hewlands gearbox myself, Mk.8-Mk.9, in FF.
To all of you guys out there, Dogs, are not Synchros. They couldn't care less how you wanna shift. They will shift like their design permits them to... period.
A few more bits, since Hewlands of that era used Cam & Pawl diffs, both of the Diff Range, Power & Coast, should be 0.90 or 1.00. They where open at constant speed. The second any kind of torque was applied, one way or another, they fully locked up. The Hewland PowerFlow Salisbury LS diff appeared roughly in the middle of the 70s.
******************** EDIT ********************
I'm in error !!!
I wrote "both of the Diff Range, Power & Coast, should be 0.90 or 1.00"
Correction : "the Power Diff Range should be at 1.00, fully locked, and the Coast Diff Range to zero as these diff had no possibility to apply any lock on deceleration."
******************** EDIT ********************
And Diff ratio wise:
©Hewland Engineering Ltd
MAINCASE AND DIFFERENTIAL PARTS LIST
Hewland DG300
CROWN WHEEL & PINION 8:31
CROWN WHEEL & PINION 9:31
CROWN WHEEL & PINION 11:38
Hewland FG400
Crown Wheel & Pinion 7:31
Crown Wheel & Pinion 8:31
Crown Wheel & Pinion 9:31
Crown Wheel & Pinion 10:31
No other.
I don't have data for the gear ratios but if you check the Retro car gears, looks spot on.
HF