You definitely have some chambering ahead of you, but a great project.
We built a midlength (7-2) egg out of maritime pine several years ago. Chambered the heck out of it, and while it was a tad heavy (okay, it was pretty darn heavy) it was fun to build and taught me a lot in my woodworking that came in handy later once I started building balsas. When building wooden boards on the heavy side, I tend to stay with shapes that forgive a bit and where drawing longer lines is inherent to the shape, hence my vote for the egg.
Weight wise, when I use denser balsa, I come into the 14 to 15 kilos (30-33lbs roughly) for a 9’6". A reasonably chambered balsa with higher quality wood usually comes in between 18 and 25 pounds, for a comparison (there are lots of variables here).
If you go for a heavier wood longboard, I suggest that you increase the vee and going forward that you keep a little bit of a belly. I’ll really help with the rail to rail transitions and make the board more functional.