The difficulty with answering your question is that it is virtually impossible to do Peny without covering the busy bits.
The route from Helwith is fine, mostly an enclosed bridleway. Takes you up to the Pennine Way path at Milk Churn.
There are some obscure routes, but you are unlikely to find them and they barely exist on the ground.
The natural extension is to walk over to Plover Hill and descend onto the Foxup Bridleway, circling back along the base of the hill. The Henry Street route goes back around the other Dale.
There are several paths that way. Though it also involves some road walking. It was very muddy last month, damn sheep were making a mess of the path about 200 yards ahead of me.
Conditions locally are much drier at the moment. Which also would suggest that the very boggy section between Peny and Plover may well be readily passable. (Lots of photos of groups traversing along the face of walls to get by some bogs..