When I brew my big double IPA, I use one large mesh bag for my 90-30 minute additions. the rest go directly in the kettle without a sack. I start with 8gallons of wort and finish with 6.5 gallons. After 10 oz of dry hopping I easily get at least 5 gallons into the keg.

Awesome. I will pick up a mesh bag tomrrow! Thanks for the detailed response.

Update on the Pliny: Just finished carbonating the beer and it turned out fantastic, as you all predicted. I sparged 14 gallons and used a slow, rolling boil, like Jamil says. After transfers and dry hopping, ended up with 10 gallons in the kegs! I used a hop bag for the first (6 oz) bittering addition but dumped the rest in freely (pellets) at the appropriate times.

My only mishap was over-correcting my pH (down below 5 with phos acid - dammit!) which, I believe, led to a decreased mash eff. OG was 1.065 instead of 1.070. Not too bad.

Thanks for the advice.