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The principle behind the serrurier truss is that the poles have to be designed such that as the telescope tilts at odd angles, the top-end and bottom-end both sag by the same amount with respect to the middle section supporting them, so that the alignment of the telescope is maintained and there is no lateral displacement of the top-end with respect to the bottom-end.
On anything less than a 20" scope however the truss is invariably so rigid that any sag/flexure is non-existent, and the truss is more about saving weight (compared to a continuous rigid metal tube) and portability (large scope disassembles to fit in car).
So in the GSO efforts (and most amateur efforts) are just "trusses" - not really Serrurier trusses - because they are made from stock tubes, with no real mechanical engineering analysis regarding sag/flexure/lateral displacement.
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