I have compared the 2, and the only specced difference I can see is that the 3299 is specced to handle up 125 degrees C while the 3296 is specced to 150 degrees C. But I will add it as another option on the list.
Actually, I am more concerned about C2 and C3. I would seem from my measurements on screen that the 50V Nichicon Muse (KZ) and Elna Silmic II options with 7.5mm lead space will not fit. The Nichicon Fine Gold (FG) option will fit though. I do see however that there is a 35V Elna Silmic II that will fit, but that specific part is not yet available from Mouser. There is unfortunately not a Nichicon Muse in 35V available. So I leave it to the builders to make up their own minds as I believe that the Nichicon Fine Gold is a good enough cap for those positions.
Good, now that I have a nice printed copy of the top layout I can see that the 3296Y and 3299Y models of the trimpots will also fit, and is actually a better choice than the W variants since the mounting to the board will be sturdier because of the staggered layout of the pins. I will add the Y variants to the list of pots and consider the selection of pots on the BOM now more than adequate unless somebody has something else worthwhile to add.
