Extra 300
Hi,
I finished one of these about 10 months ago, the XS version. I think you'll be happy with the kit. I went the Moki 2.1 route, and I'm not familiar with the BME50, so I can't help you with T/W questions.
Mine weighed in at 15 lbs 1 oz final weight. I built mine stock, but increased the size of the lightening holes, and added some more. If you want more weight out, alot of people have mentioned replacing the spruce spars with balsa, and stuff like that. Keep the model light.
You're right with the hardware. I replaced all of my hardware with what I'm used to using. I forget what tailwheel I used - it has a single black leaf-spring type support with spring pull-pulls on the tailwheel, going to the rudder horns.
I've heard of these kits flying anywhere from 14.5 to 18 pounds, with varying amounts of performance.