If anyone is still doing this take a look at this concept for getting rid of the center piece, I'm trying to get the printing time down to 15 minutes an end or less so the filastruder people that are printing in bulk can use it.

Search 'rtrski' on Thingiverse and they should show up.  I sized them for the type of spools you get from Solidoodle (the tall, narrower diameter ones) vs. the short, high-diameter one I got from Protoparadigm.  But if you import the STL somewhere else I'm sure it's easy enough to bump up the outer diameter to the 2" or so for the larger diameter spools.

I like your spool design, by the way - have you ever tried just dropping a neatly-wrapped loop over the hub, then assembling?  I've noticed my ABS has enough 'stiffness' that about half of it is semi-unwrapped from the spool anyway once I start printing (especially using bearings so there's very little rotation friction) but as long as it doesn't stray over the edges of the spool, it doesn't seem to tangle.

The print really was to test a few things;

would such a large part stick to the bed ok? yes - too well on the print just with kapton, perfect with glass
can i make a thread that works? yes
will my black filament screw up and block the nozzle yet again? no it didnt, and im really confused .. ive printed for about 14 hours almost constantly with it now with no issues, so im a bit confused.

I can post the SCAD files for them if anyone is interested. The two parts screw together, so in theory, you can put it together and take it apart many times without any issue. The other question would be why you would want to do that? the answer is i have no idea, but its cool anyway.

can you take a photo on the bed so that we can get an idea of the size?

(I've shown one half of the spool being printed, for measurements, the spools outer radius is 65mm (i.e is 130mm across) pretty much all the usable area of my bed before I hit a warped low spot and have trouble with sticking.

I think ill reduce the amount of plastic in the spindle next time I printed it with only a small amount of support, but print times could easily be improved (by a lot).

edit: my printer needs some serious calibrating

There are a couple of prints that might interest you then.

first disclaimer, the spools that these STL files make are close tolerance fit parts, it is difficult to get them to mate properly, and you DO need a well calibrated printer.

Firstly, here's the "rich mans" spool, there is a small hole at the centre to poke the tail of the filament through for winding it on.

(you can see that the top has a small raised boss to make the mating of parts more secure.)

(i've poked both ends of the spool into the little hole so that it doesn't all unravel)

Secondly, the "poor mans" spool, which uses a lot less plastic to print.