I`ve got a vague recollection that Ivan Pettigrew may have done one. He has plans for a Solent at 82" span for 4 400 electric motors. www.geocities.com/ivansplans
The Sunderland on Geoff Reichelt`s site was based on one by Dutch modeller Jan Hermkens and is/was a RCM&E plan from nexus Plan Service (UK). Might be a good starting place for a reverse engineering excercise. Do you know if the glassfibre Reichelt Empire boats were produced for public sale ? Just dreaming ...
then a Mercury/Maia composite!!!!
If you want a read of Brian Cassidy`s book "Flying Empires" mentioned on the Reichelt site PM me.