Don't reinvent the wheel, Tim and I have had Logo's on our sails for over a year and can answer most of your questions.
Vinyl type will stick to Mylar type sails OK. Lasted about 6 months on Dacron sail didn't seem to stretch with sail when I landed on it! So I think sticky back sail cloth (like numbers) is best for Dacron sails. It can be cut in vinyl cutters. The actual Logo is difficult to apply and I would advise soapy water on Mylar sails to allow repositioning. On Dacron it doesn't stick as quick just be careful. A screen printed Logo on a background would be easier to apply but I think the Logo on it's own looks better.
If you already have a class logo Taipan etc. Placement near clew I think looks good and there have been photos of Mossie sails on Forum with logos in position.
If you don't have a class logo other than F16 then placement following ISAF guidelines as found on Alterd's main, see attachment and on Ben's main in recent photos on forum is going to reduce the chance of problems at reggattas.
Generaly placement of Starboard side highest as per ISAF guidelines is best as back to back nearly all sails can become transperant in some conditions and cause cofusion of logo.
