So I'm trying to print a couple of pretty basic files. They're the biggest and longest prints I've tried so far. But very simple.
The part on the print bed are hollow rectangles 52x42 mm with 5mm walls on the bed.
Not enough to warp and should be plenty too keep them stuck to the bed. Both are just about on the max printheight - around the 140mm mark.

But should not be difficult prints.

I'm currently using pet tape heated to 60c and pla. Which for any print under about 3 hours has been very very good.
This is the first real issue I've had with the tape and sticking.

What I'm finding with these big prints is that the bloody things are detaching from the build plate at about the 4-5 hour mark (judging by what's printed and the amount of loose plastic in the case).
It's not the pla. I switched from cheap ebay pla to polymakr polyplus - with not real difference (less warp, but same final result). There was minimum warp, the bases are super flat with a very slight squish - proving the calibration is super tight.
I've tried slicing with simplify 3d and makerware - doesn't make any difference.

So how do I make the tape more sticky. Think I read you can use a gluestick on pet tape. Are standard gluesticks okay (pretty sure I've got one in the 3d printing bits and bobs box). Or do i need some kind of special stick ?
And what temp works best for them ?
I don't care if I have to remove the tape with the print, just so long as I can actually print it.

Help ! :-)