Rob, for comparison purposes, my machine is roughly1800x1000. The gantry is built from the equivalent of 4m of 50x50x3 box section steel. Then there's a couple of 20mm Ecocast plates, about 450x200, plus weight of ballscrews, motors, spindle, etc. I'm probably looking at around 50kg for that lot - I keep meaning to work it out but haven't done so yet. It's all driven with two 3Nm motors via twin 2005 ballscrews and 1-1 belt drive. The inertia of the ballscrews is a much bigger load than you would expect and makes weight-saving a lower priority. I get 5m/min rapids with reasonable acceleration (important to me as I end up doing a lot of small fiddly work). By bringing the length down you might be able to go to 16mm ballscrews which is a great inertia-saving measure in itself, and I'm not sure I would bother chasing the odd kilo here or there. Unless you want the cutouts so it looks pretty, of course!