I can build contest airplanes all day long with the current stash that I have. However, since getting back into rocketry, I have realized that I don't really have much wood that is > 8 lbs/ft3.
I have spent so much time and energy on locating a securing contest grade C-grain balsa, that I have neglected the medium and above balsa almost to exclusion.
I was in my local Hobby Lobby yesterday and noticed that they had finally restocked their 1/16" balsa. This stuff comes From Guillows and looks like the wood that you would find in a 1970's die-crushed model airplane kit. It was dark and heavy. I picked up 6 sheets of mostly C grain 1/16" with none of it less than 11 lbs/ft3.
I was unable to locate my scale when I went shopping, but it isn't a big deal when you're actually looking for heavy wood.
For those of you looking to get into shopping for balsa with a scale, the Bradley brothers have created a couple of nice graphs that will give you ballpark density numbers given the weight of a sheet of wood. I use that while shopping. When I get home, I make more accurate measurements and write everything down along with a computed density on a piece of masking tape which gets attached to every sheet of wood in my shop. When I want a piece of wood, I merely go through my stock looking for the right density and grain.
You can find the density charts
here
I have also attached a spreadsheet that I keep on my google drive. I can then access it from my phone to calculate balsa density whenever I want using Google Sheets.
Stan