Best sellers & related products conflict

using joomla & protostar template, I am trying to use the following two modules "related products" & "best sellers"
I have 2 categories and several products within each category
ex:
home->products->category A-> <product 1,2)
home->products->category B-> <product x,y,z)

relationship
Product 1 - product x, y, z are accessories for Product 1
Product 2 - product x, y, z are accessories for Product 2

on the products page
I want to show "best sellers"

once you select a category (A or you then have product list page
here I want to show "related product" (list showing x,y,z)
and the same if you select product 1 or 2 on the product page

in all examples, best sellers or related products are in the left position

the problem I have, is if I turn both on and assign to left position, best sellers shows up products, category and product pages and related products only shows on product detail page, in center position.

in menu assignment, I've done the following:
best sellers = products
related products = category A & B
menu structure is
home
products
- category A
- category B

I don't see a way to add product pages to structure to direct assign modules

thanks for your help,