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We actually worked on a system very similar about 7 years ago, but never brought it to market. We have discussed going back to it at some time, if there is enough interest in the product. Right now though, we do not have a solution available for what you are looking for, in regards to the spacers.
In regards to the movement, do you have the Idler Arm on the single leg side? Do you also have the 3' Idler Arm? The 7" Idler Arm is meant for when you want to use the K-Pod on standard 24" wide doorway dolly track, otherwise I would recommend the standard 3' Idler Arm as it tracks along the curves of the track better. Thanks.