With regards to tapering of the forestock, I've found a few things to be helpful. Of course starting with a barrel pattern having a good sized breech is important. I'm not familiar with many of the commercially available smooth bore patterns, but my impression is that the breech size on many is on the small size, especially when comparing them to a typical English barrel of the period. The stock pattern along the lower toe can be designed such that there is a decent amount of height at the breech area as well. Finally, one of the most important factors is to position the ramrod groove very close to the barrel. As little as 1/8" can be good. It is not uncommon to see the groove follow the barrel on original guns of the period. This creates a relatively uniform web thickness along the upper forestock. With a barrel having a large breech and small forward section, it's necessary to bow the stock slightly while drilling the hole to prevent the hole from running too high, if a groove is set up this way. It's really no trouble though. After studying some English fowling pieces closely and building a version of my own, this is a practice I've been following even on some longrifles I've built. I think it can add a lot of aesthetic appeal, especially if the wrist has a fair amount of taper toward the comb as well.