These are the spacer blocks i designed to work with the aluminum build plate stiffeners sold by rc-lohas on eBay.
He redesigned his brackets and they now include holes for the screws that go though the back of the Z-Axis arms. If he doesn't have any for sale on eBay send him a message as he's probably out of stock!
I helped him with the measurements on these and got the first couple pair made and installed a pair on my CTC, they will also fit Flashforge, Wanhao, and the Makerbot Replicator 1, i assume they will also fit the Rep 2 as the arms appear to be the same. Good quality and really do the job for keep the arms straight.
You will need 6 - 3mmx25mm screws, and 10 flat washers. The stiffeners come with four screws and allen screws for the adjustment. The washers i used are sold as rivet washers at most hardware stores, look for the pop rivets and rivet tools. These are about .75-.80mm thick and give just the right spacing. My local stores only carry 3mm screws in philips head so thats what i went with.
Put the spacer on and then the aluminum stiffener, install the two side screws into the platform, just lightly tighten them so they can still move a bit to allow the bracket to slide front to back, then install the lower back screw only to act as a pivot point and install your two allen screws that come with the stiffeners. Tighten them so the allen screws are flush with the hole, this will force the upright portion back and straighten it and also line up the other two holes for the bracket. One my one side the hole was centered front to back but not top to bottom, slight variation in the castings, so i just cleaned it out with a 3mm drill bit.
After installing the other two back screws tighten the two side screws and your done!
To do this you really need to remove the build platform from the printer, but its not that hard it literally takes me like ten minutes to pull one of these out by unscrewing the Z-Axis motor mounting screws and removing the top Z-Axis bar plates, unscrew the motor from the platform and set it aside, pull the two Z-Axis bars up leaving their lower mounts in place, remove the platform, reinstall in the reverse order.