I believe that the reason we post our work is to get input from others. Your workmanship looks really good. This is just my opinion. I think that the mini 500 transmission and rotor system is going to be too small for the size, weight and power plant. A winters non quick change with a larger ring gear than the mini for a transmission and a Rotorway head may be a better choice. The blade span of the mini may not give enough disc area. Your blade span may need to be around 23 to 24 feet. There has been plenty of helicopters that have been built that are similar in size and power plant, they already have it figured out for you. if it worked for them just copy what they have done. Again just my opinion.