Angus, I didn't want to introdue the IMAC argument, but they can sure spend a LOT of money on their airplanes!! I agree, you can build/fly a competitive pattern ship for much less than $8,000 (especially if you build it!!) and I don't think cost or size has deterred anybody from participating. The larger pattern ships may be more of an attraction today!

How long has the 5Kg limit been in place? Since the original rules?

How much does an electric propulsion system weigh (motor, speed controller, battery, motor mount, and any other paraphernalia)?

How much does a glow propulsion system weigh dry (YS 1.70, mount, exhaust system, tank, fuel tubing, fuel dots, mounting accessories for exhaust sysem, etc)?

Don Lowe wrote an article about weight and pattern ship performance (especially in regards to damping in 'heavy wind'). He concluded that lighter is better. If current designs need to be light for calm conditions and ballasted for wind, then perhaps a better design is required...