you could check the dimensions of the manufactured battery and mock up a cardboard one to see if it fits ok, but ill give you a tip, and suggest go w a custom battery, spend a bit extra, its worth it for the higher quality cells/reliability and smaller size/weight. often mass produced batteries arent high in quality and the plastic casing makes them too large and bulky. https://bicyclemotorworks.com/product/52v-16-8ah-molicel-p42a-high-current-lithium-ion-e-bike-battery/ is the best newest battery technology you can get, just released, should fit that frame no prob. good luck