I Sail Cat rig with a Landy Spinnaker. A longer pole gives me a sheeting angle between the shrouds and front beam so whilst gybing the sheets only have the resistance around the fore stay. Previously with an Ullman Kite and shorter pole the kite blocks were fixed near the centre board casing and therefore there was more friction on the spi sheets around the shrouds. That was my main reason for lengthening my pole. I suppose I should really contact Landenberg to find out what the optimum angles and measurements are in this respect as I guess your kite was custom designed and manufactured to your needs.
As for making a difference to the boats speed I haven't got a clue, I would imagine the sheeting angle and luff tension are more critical than the distance of the clew from the mast foot (pole length).