RE: Adding winglets to ARF wingtips
It sounds to me like you are just going to add more weight to an already heavy airplane. There is no fix for heavy other then weight loss. On an airplane like this 1 pound can easily be lost just through careful selection of equipment. BTW do not fly without a cowl, the poor aerodynamics resulting is not worth the weight loss there. Post detailed pictures and I will come up with at least a dozen suggestions for losing weight.