I think that many will agree that the MFT/3 is one of the most used tools that Festool offers. It is a key component of the overall system and enhances the tools and work processes. By itself, it provides a great work surface with a lot of clamping capabilities and much more. The Festool engineers have figured out a way to make a great tool even better with the Cross Member supports.
The MFT/3 is a stable work surface, but it is subject to some side-to-side movement during certain applications and the cross members really add a lot of rigidity to the entire table. Included in the box are two round steel legs and some angle pieces that attach to the bottom of MFT/3 rail. The legs are 25 5/8 inches long and fit into plastic clips that attach to the bottom of each leg set.
These are bolted to the bottom support piece of each leg set (one on each side) with a plastic connector that allows the legs to pivot into place. At the top of each leg set there are two plastic thumb screws connected to a pin along with a spring mechanism. To install, you push the spring mechanism in, which exposes the pin and you then slide the pin into a notch in the angle piece. Tighten the knob a few turns and that secures the cross member leg to the table.
Each leg also has a plastic clip that clips to the leg support. If you need to pack up your MFT/3 you simply unscrew the knobs that connect it to the angle piece, rotate the arm down so that it is parallel to the cross piece on the leg set and clip it into place. This locks the cross member securely to each leg set so that you can fold the legs down for easy transport.
You can install the cross members on either the front or the back of the MFT/3. Since they are close to the edge I find that they do not get in the way. It is good to know you have options in case you use the space under your MFT/3 for storage and you will need to account for this in the install. I have mine up front and that works for me since I move my table around and often have things behind and underneath the table. Keeping the members in the front allows for me to push the table against something and not have the cross members get in the way.
I have found that the cross members really do make the MFT/3 more rigid and I think that it is worth the investment. This is not to say that the MFT/3 in its standard configuration is not a secure work surface, because it is. The cross member supports just make it even more solid and stable and I think it leads to a little less vibration. I would not use the MFT/3 with or without the cross members for any heavy duty hand plane use as I do not think it was designed for this type of work. But for a general gluing, clamping, sanding and power tool station, it excels and the cross members do help increase the stability of the MFT/3.