I've been training to do this as well -- But my goal is 36 hours. I made an attempt last week, but got dehydrated and I decided to bail at Mowich once it started raining. I'm going to try again the next full moon. Some advice:
If you have support available at Mowich and Sunrise, the run becomes substantially easier. My plan is to do it self-supported though.
There's lots of water on the trail, so you don't need to carry too much. Last time, I started with 3.5 L and carried iodine tablets. Next time, I'm going to carry less and bring a filter. The filter costs less weight wise, because when you stop at a stream you can always drink the weight of the filter immediately instead of waiting a half hour...
Regarding food, I took 60 shots of GU (4 gelflasks, plus 8 refill packs), 2 bear valley powerbars (some protein and fiber), 3 PBJ sandwiches, plus 20 oz of gatorade mix. Next time, I'm going to take about the same, but perhaps 2 or 3 packs less GU.
I took about 12 lbs of gear including shoes, clothing, poles, etc. (+ 6 lbs food, +8 lbs water). My bivy system consisted of a FF helios jacket, shell pants and a cut down 3 oz blue foam pad (and a loaned tarp from the ranger at Mowich Lake - Thanks). Next time, I'll bring a light bivy sack and sleeping bag, just for the security of being able to stop in comfort. A 40 degree night in the rain with the gear I brought is easily survivable, but lower in the comfort scale than not stopping at all...
There are parts of the trail where you won't want to stop because of mosquitoes. If you keep moving, they have trouble keeping up.
Regarding timing, I hiked the uphills at 40 fpm, and ran the downhills for an overall average of about 3 mph (some stops). You don't have to move too fast to make it in 48 hours, just keep going...