You can run a feeder line of the 19mm poly and use 'starter elbows' instead of 13mm tees. You just punch a hole in the top of the feeder line with a special tool, push a fitting into the dripline, and then push the fitting down onto the feeder line until it clicks. Do the same thing at the other end and it will save you a heap of time. The pipe can then swivel if it is moved so there is more flexibility.
Nice job btw.