Alpin: The EVO 80 will generally speaking be similar to the Guerilla you have, not really feeling much smaller. The Kode 80 is a far smaller feeling board, in fact more comparable to an EVO 75 if you want to go EVO. But if you do a lit of high wind lake riding, I would say the Kode 80 is the best choice. It's excellent for that and a great wave board too. Maybe it will feel a tad overloaded with a 5.8 though. A way to proceed would be to get teh Kode 80 and keept he Guerilla, and then if it works out with 5.8 for you on the Kode, sell the Guerilla later. There is also the option to go Kode74. It's not that much smaller feeling, but still more controllable with a super powered up 4.2. But then you would for sure need the F2 for 5.8 sailing. And even in a two board quiver, its not that evident that the 74 will be better. Sometimes some overlap is good and you will only sacrifice a little top en control but will be able to get on the small board quite a bit earlier with the Kode 80.
Shimeone. Hard to say. For light weight, EVOs can be a bit wide as high winders, but manye heavyweight swear by them particularly for high wind use. It is like the extra wide platform give the little extra carrying ability that you may need also in high wind since it's generally gusty. As noted above, the Kode 80 is for sure also a one class smaller board. So even though technically the Kode is the best high wind blaster, I would go out in a limb and say the EVO 80 might still be the most practical board for you.