JBP 2nd Trunk chop

This is a 14 year old tree, started from seed, grown in a colander and put in the ground about 6 years ago. It is vigorous and will one day be a very nice formal/informal upright (I hope!).  I am currently in the process of trunk chopping it down to about 18inches tall.  I made one chop two years ago at the spot marked.  It has recovered vigorously, and now I am ready to go to the next chop.  My question is, can I take it all the way down to the second black line in the photo?  It will lose 30-40% of its foliage if I do.  What are some factors I need to take into consideration before doing a second chop?

Can you chop it to the lower point? Looks like you could, so from the photo I would say yes. There appears to be enough foliage below to keep the tree healthy.

Safe - don't remove more than 30% of the foliage in any one pruning.

If you are brave, and have good aftercare - you can probably go to 50% of foliage, but this is not risk free. More than 50% is quite risky, but if your aftercare is good, you might be able to get away with more.

Should you chop?

I would not chop the top off until the trunk, just above the roots is the diameter I envision for the finished tree. Once you start chopping the tree, the trunk will cease to thicken at a useful rate. There will be slight, slow thickening, you need lots of foliage to thicken a trunk. So you need to think about your future goals, then decide if you should chop. Your finished tree most likely will be composed out of the the growth in one of the branches in the first whorl of branches.

For a pine of shohin size, I would shoot for a trunk that is at least 2 to 4 inches in diameter (5 - 10 cm), for a tree around 12 - 18 inches tall (30 - 50 cm) I would shoot for a trunk that is at least 3 inches (7.5 cm), preferably 4 inches (10 cm), and could go up to 8 inches (20 cm) in diameter for a thick squat tree.

So think about where you want to end up. Then decide if a chop needs to be done or not.