Do not overcomplicate this one.
Do not allow the loop portion to dictate the length of your upline. The length of your upline will dictate the size of the loop. Of course, you do not want to pull a 30 foot diameter loop, but do not get carried away and end the upline at hourglass altitude. If you make your loop to big, then you will probably end up outside of the end marker and zero the whole manuever.
This is a case of where it is easier to fly than to draw.
Mark