We are looking to make a riser plate for our Vertical Milling Centre. It is pretty simple, a couple of T-Slots and alignment holes (2 1/2" X 24" X 16"). We will face it in place to get the highest flatness possible. The purpose of the plate is to help us reach material with short tools as well as acting as a locating feature for quick change components (we can make alignment holes and slots without attacking our machine bed).

We are not sure of the best aluminum based material (has to be light enough for 2 people to lug around) for the application. MIC 6 would be perfect except that its strength is so low we are concerned about cracking the T-slots. Is there another reasonable cost material (aluminum) option that has low enough residual stresses to stand up to facing and T-slots without warping AND has a decent strength?

I've heard of Wrought Tooling plate but have no experience to tell if it will work or not.