Are your rims clean. A stock exhaust will get oil on the rear rims and make the brakes useless.
Check the alignment of the pads against the rims. Most have some adjustment so the pad gets full contact against the rim. You'll want as little clearance as possible between the rim and pad.
What pads are you using. The harder the compound the harder the braking action. They'll last longer than a soft pad but require more pressure to stop you.
200lbs isn't too heavy for good brakes. You're weight isn't the problem.
I know you said you don't want to spend more $ but, if you want the best brakes possible, go with discs.
Tom