Viking Arm 3mm base plate

I bought the 3mm base plates for the Viking Arm tool to allow me to use it on decks & for use in gaps of 5mm or less, which are fairly common. I fitted the 3mm plates, which also have a much smaller footprint, in place of the 6mm plates to the unit I carry with me always. I had a 50kg solid entrance door to fit within days of putting the 3mm feet on. The door opened over a stepped down floor - so the air bags were too small to lift a door that heavy into place. I used the Viking Arm, but found the clamp to be less stable on the ground with the smaller feet, so it wanted to rock back as the door got higher, once it did that the moving plates, having a smaller bearing surface, marked the bottom edge of the door. I ended up using an air bag to keep the door stable on the latch end & the Viking Arm to lift it at the hinge end. I think the 6mm feet would have been better in this setting.