Typical RC usage has short engine bearers (or bolts the engine to the firewall), but typical RC usage has fuselage doublers going back to the wings, too. I know that my Nobler brought the engine bearers back to the wings, but had no doublers at all. So I think that both practices are providing strength where you need it, just in different ways. I also suspect that the Control Line way of doing things is lighter, but I couldn't swear to that without some serious consideration.
Tapering the engine bearers starting right behind the first former and going back to where they end sounds like a good idea to me, as does drilling lightening holes in them behind the same former. My knee-jerk reaction to the tapering is that it'll work better, because the formers will tend to flex in the back, instead of snapping, or snapping the fuselage wood. But I don't see that done much -- so I don't know if it's a good idea or not!