Looks awesome! Really nice job thus far
On the question of painting the frame - you absolutely need to finish it some how. Powder coat, Paint, lacquer or anodised - if you don't the aluminium will dull and then begin to corrode quite badly, especially if you take it near salt water in its life.
Aluminium is an awesome material but if it's going to get wet it needs to be looked after. I'd advise anodising it if you want a bling finish - but there's some sweet powder coat options available too these days (metallics etc)!
Hope that helps a little, keep us updated on the progress!
Mike