Uplinker,
After the bankruptcy of Rolls-Royce in 1970, the only suitable engine was the modestly powered (6500lb thrust) ALF 502. Unfortunately, this resulted in four engines being required instead of the original two. Certainly wasn't due to splitting-up generators and hydraulic pumps due to lack of space in the nacelles.
The reason the APU is (sometimes) used for take-off/landing is simply because the engines aren't powerful enough to provide bleed air for: i) the packs and ii) the airframe ice protection.
Regarding the loading, you might find the dispatcher on knobbygb's flight had screwed-up the load-sheet. The longer version (146-300/RJ100) isn't as trim sensitive as suggested.
I usually tell people I flew the 146 despite having flown the RJ100. This is because most people think of cheap little bendy aeroplanes from the Brazilian jungle when you say "I used to fly the RJ".
