I think 53 would be too tight for your racquet, depending on which gauge you have. In my 345g, 95", 18x20 Biomimetic 200 racquet, I strung Lynx 17 yellow @50/50 (drop weight) and it felt comfortable and right in the heavyish racquet. I tried it again in the same racquet @52/51 (electronic stringer, so a pound tighter between tensioners). It felt too tight to me. With your lighter racquet, I'd recommend stringing between 48-50, unless they're making the Radical MP as a 16x19 now. In that case I would start @50.