Improved Isp Rocketry II

Two questions this time:

1) Is it possible to get kerosene-LOX or propane-LOX to 395Isp? I've
seen numbers around 360 on www.astronautix.com .

2) How effectively do large, altitude compensating nozzles
(particularly aerospikes like on Bono's Rombus) maintain specific
impulse between sea level launches and orbit? For example, would it be
reasonable to maintain a LOX-propane specific impulse of 350 between
the ground and orbit?

Mike Miller, Materials Engineer