the lock diff setup came about when they had the Reedy race (I think?) where Mike Reedy announced therell be no oneways only diffs.
so the AE guys came up with locking the front diffs to get more traction on power like the oneways without braking the rule of no oneways.
At the same time they tried out the use of rear shock tower and new arms.
I had a chance of using the rear arms in the front years ago(run out of arms back then)it gave the car a softer front (wish I had the Idea of puttin that extra hole!)

so I think using a solid diff is a better Idea than a lock diff.
I have manage to modify a NTc3 solid diff (bec its longer)
but I havent put it at the track yet.
you dont have to worry about it gettin loose
and best of all you have brakes on the front

there are track layouts where a oneway is a better weapon.
the lock diff is another weapon for you to have for your disposal
I have tried the lock diff,new arms,shock tower and foams so far this is the nicest setup I have tried.
thats why I opted to bring it to next level and use a solid instead of lockin it.