Wouldn't it be better to wait until you find out what he has before spamming him with confusing adverts.I usually fit BBS01 to trikes and set the speed limiter to 12mph.
The hub kits are not ideal when you ride at very low speed.
https://wooshbikes.co.uk/cart/#/product/uid-164-bbs01-13ah/bbs01b-cd-kit-with-13ah-36v-hl-battery