Thanks David (and Joe) - that's a hugely instructive video. Much appreciated. So user friendly.
Would be dead interested to hear the details on the green strip - it'd need to be pretty resilient to both grip and at the same time stay flat against the edges of the platens so that it wouldn't knock the piece out of square. Is it possibly part of a kit?
One very nice feature is that if you cut the platens on the saw after fitting the rail that drops into the T slot on the slider is that you end up with a perfect reference for where the saw cut will end up. You could also organise a vertical knob/handle with a threaded end passing through the platens into the T nuts - that would make them capable of being locked down. Maybe even the equivalent of a sliding stop mounted on the platens too if it turned out to be needed/udeful.
It'd also be possible to make a version where the platens were quite wide - so that it could handle fairly wide cuts up to the point where stuff becomes wide enough to locate accurately off the cross cut fence.
Wonder if it makes a set of parallel bars redundant?
ian