first post of many i'm sure...

I'm making a kilt for my boyfriend, but I have a question before I start cutting (and really before I get final measurements).

All the pics of people wearing kilts have them wear it high on the waist, like above the navel. But my boyfriend has a bit of a belly and normally wears his pants below it. So when I was measuring, measuring & measuring, there is quite a difference between back-side-and front for the length.

I want the kilt to come to middle of the knees as that seems what most instructions say, but I'm afraid it'll be much lower if I use the front measurement. But he's losing weight (20lbs so far) and I'm hoping to take it in when he's at his happy weight, but I dont want it to be a mini-kilt when he can wear it higher on the waist.

So long story short:
What is the best way to measure the length and is it ok for him to wear the kilt below his belly like he does his pants?

Thanks
Kitty