Mate, just about any size will fit behind a 1200 grille. If you're main aim is good value for your dollar (which i assume it is seeing as though you're wanting FREE advice haha) I had a cooler that was a little over one meter in total length including end tanks and it was all behind the grille. That was with a CA18det.

unless you are planning on conquering the world and need every last advantage of a 'custom' cooler i'd jump on ebay or look up just jap. They are cheap coz they are mass produced using chinese labour. they also weigh a little more but are still great coolers and can be had for as little as $100!

bar and plate, tube and fin... they are just different designs. its the restriction inside the core that is more important.

good luck!