Obtain Simple Product from within shipment at requestToShipment

I’m working on a custom shipping module, and require data from a simple product that’s a child to a configurable product when processing a shipment. Therefore in my module, I have a Carrier.php that extends MagentoShippingModelCarrierAbstractCarrier, and in there I have the method requestToShipment. However I am struggling to obtain the simple product data from within this method.

I have tried using $request->getOrderShipment()->getItemsCollection(), however this fetches the configurable product IDs. Therefore I’m unable to reliably link back to the simple product without mistakenly targeting an incorrect product.

I can make use of $request->getOrderShipment()->getOrder()->getItems(), which fetches both the simple and configurable products. However I’m back to struggling to link it to an item within the collection from the order shipment.

Finally I have tried $request->getPackages(), but again this only fetches IDs relating back to the configurable product.

So from either one of these loops, how do I obtain the actual simple product object relating to that package/order item?

Thank you!