I had the same concerns when I went to the SL, given the boat is > 1k heavier than my previous Mojo. I stuck with the 400 given the advise of some forum members, and I have to say, I am glad I saved those 8k$. The 400 pulls my SL weighted with full ballast and crew like a champ. I am yet to find an instance where I was left wanting more power. I live in central Mn. And surf quite a bit at Gull lake, not sure what elevation is. The new gear ratio and the prop adds more torque.
At 1000ft, I'd say stick with the 400 and put that money toward adding every single option you can. Load that puppy up.
Or get the Mojo. I loved that boat. Only problem is no subfloor ballast. I have to say, I really like the subfloor ballast thing. Sooo nice to preserve storage. You don't realize how nice it is until you have it. The SFB would be the only reason I would pick Makai over Mojo. I like the spray pattern of the Mojo better also.