George,
I am not a racer, so others with some more hands on experience can provide some better details, but the solid axle should have some benefits and drawbacks compared to the diff. It can be a trade off between on power steering and acceleration vs off power steering. I know that Ralph has always said that the solid axle requires a more aggressive use of the brakes in order to get the car into the corner, without using brakes the car will push.
There are still some tracks where the team has preferred the stock diff, so the lightweight spool isn't necessarily the best for every track. You will need to find out which setup you are more comfortable with. Your posts about the steering blocks and drive shafts seems to indicate that you are still spending some time in the boards
. Your issues with these components are not common for NT1 customers, so there is something else going on. XRAY's parts will compare to any car's durability. I am wondering if there is something bound up in your suspension to cause the frequent damage. I have seen some NT1's absolutely beat down the track walls and drive away, so something else is causing your issues. I think I saw that James was going to be at your track to take a look at your car. Hopefully he can watch you on the track and give you some setup tips to tune your car to your driving style and track. If something is up with the build of the front end, he will probably be able to identify it.
Using the locking block in the stock diff may have a bit more 'give' than the lightweight spool, but it will still be harder on the drivetrain than the standard gear diff.
Bryan