Problems with TPU (nGEN Flex)

So I've been trying all day to print a simple part using Colorfabb nGEN Flex filament. The filament itself prints well, but I'm having a few problems with it. First of all bed adhesion. No matter what I try, hair spray, glue stick, etc., it will print fine for the first few layers, then start to warp and come off the bed. So my settings right now are:

H: 255 C
B: 80 C
Retraction:1mm
Extrusion multiplier: 1.25
Printing Speed: 40 mm/s
Layer height 0.100 mm
NO cooling at all

So I tried several things today. I tried increasing my z-offset to hopefully get the first layer to stick better, but that literally did nothing, even after I raised the offset by 0.07 mm. Every time I changed it, nothing happened. It seemed to extrude the exact same way. I even kicked up the extrusion multiplier to 1.50 and it did nothing to help! I tried increasing the bed temp, decreasing the bed temp, increasing the hgotend temp, decreasing the hotend temp.................nothing. I tried turning off retraction, increasing retraction distance, decreasing retraction distance, increasing extrusion width, increasing/decreasing printing speed, absolutely everything I can think of and nothing, nothing, nothing has helped.

It really prints BEAUTIFULLY though, very clean layers and excellent layer-to-layer adhesion. I just really need to get it to stick to the bed better. Colorfabb recommends printing on Buildtak, but I refuse to print on that surface. I haven't had very good experiences with it. Most of the time, the print sticks to the Buildtak so much that I have to pry it off with every ounce of strength I have, or even hit it with a hammer (for PLA and ABS anyway). I print on glass only. As a matter of fact, my prints were crap before I started printing on glass.

Has anyone had experience with this? It doesn't have to be nGEN Flex, just TPU based filaments in general. I would really appreciate any insight. Thanks.