It's funny you mention this, because I was having similar thoughts about running a smooth rod through the front. This will really only be feasible if the holes up front are 13mm like the ones in the back, but not near my machine to check. If they are, you could put a smooth rod up front and put the pulleys on it, and put the rod on flanged bearings. Two advantages I see are it may strengthen the frame some, and stiffen the Y axis some more, which are both good things. A couple disadvantages I can think of off the top of my head are its simply more complicated (adds another step to belt alignment), and could end up being a potential source of binding if there are things I'm not foreseeing. I don't think it would need pillow bearings, because the belts shouldn't be tight enough to bend the rod toward the rear. Just some thoughts. I'd be interested if you tried it out and posted your results.
From your other threads I see that you are more than happy to modify your machine. The drive system needs a LOT of work out of the box-look into the Lawsy carriage, and consider strengthening the rear rod with a pillow bearing and flanged bearings on the sides of it. I'm still working through this on my machine (finals week), but I've loved every single enhancement I've made to the drive system. My thinking is your prints are only as good as your drive system, and while the stock drive system works, it's simply adequate. Nothing stellar. If you cherish dimensional accuracy like I do, there are a lot of things you can do to really tighten up your machine, make it run smoother and ultimately print more accurately.
The stock idler brackets will work, but you should print your own once you're up and running because Solidoodle printed the parts for your printer at low infill, likely somewhere around 30-40%. (At least tbey did for my SD4). Search Thingiverse.
