I have a shrub riser that waters a Japanese Maple and I have attached a drip adapter with one side barb and have attached one section of mini soaker hose.

The soaker hose doesnt seem to be doing much.
I suppose I should use the Poly tubing instead but have no experience with it. Most of what I'm trying to water is a very narrow strip of Lirope and one small area of seasonal color under a small tree.

Is there a maximum length of the poly tubing and/or number of drip heads?
How do I space the drip heads in the poly tubing and how do I affix them to the tubing?