hard or soft copper line for a valley oil gallery bypass line?

I say it doesn't do what they say it does. And it doesn't. If you are using it to put oil back to the lifters for pushrod oiling that's one thing. But saying it slows the oil down defies ALL logic.

So you tell me what the OP will gain if he wastes his time and money doing it.

I'll tell you I called in a late night favor last night to a guy who knows things. Without me going out to the shop and taking some measurements he did some rough calculations. His math says it doesn't slow the oil down. It can't. He and I were looking at the oiling schematic and he thought the whole thing was retarded.

If you are trying to get more oil to the bearings, and by blocking oil off where its not needed why is it going right back to where you just took oil from? That makes no sense.

To that end, the oiling going to the top end, especially with a roller cam that has a groove in the 2 and 4 cam bearings to get full time oil to the rockers is what is taking oil from the bearings is what's causing oil loss to the bearings, not some fantasy about oil velocity too high.

Just because Chrysler developed it doesn't make it right.

For the OP its a giant waste of time and money. Why people ignorantly defend this modification is beyond me.
I agree with your last statement. It is beyond you. Deniers do not want to admit that it works so there's no sense in even trying to convince you otherwise. Just do the modifications and see what happens.