yeh wheels are the worst place to add weight, the major one of unsprung weight making the suspension work really hard and it'll cause the tyres to struggle to keep in contact with the ground. then there's the rotational mass as well, rotational mass on the wheels will work the engine harder trying to accelerate and make it slower and once they're up to speed they're harder to slow down as well so your brakes are worked harder too. some lightweight 13's are the best way to go, and in my opinion 13's are the perfect size for a 1200
know what you're sayin about ca's and stuff as well, a car that handles is much more fun to drive. even though mine is a heavy dirty ca20e with barely 50-60hp atw i still lapped my mates 240hp atw celica best feeling ever passing him twice in one session