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Why on earth somebody use SOFT wood as mast core. Most racing mast are solid carbon for good reason. Balsa is worst composite core in humid aplication ever. Thats why they invented PVC core. Because balsa rot. Use hardwood or bamboo.

In general
Any wood core will be much lighter than solid carbon or ALU. Soft wood are much worse in humid condition than HW. HW is much stronger in compression and shear than LW.

^comparing the weigt of wood core and solid mast one might be surprised but wood core is not that lighter when done well.
Simply coz the core is so thin to compensate for 2-3mm carbon layers, hence 10mm core will make 12mm thick mast, but 5layers are not near enough (5 layers = 1mm).

I've got both, my diy Pwood and production carbon one.
On the moisture front, surprise surprise, all TT boards are Pwood. Sure, some on the market are not.

The bamboo core mast, if built well, will be about 1.6- 1.8kg. That's rock solid. the Alu mast weight is about 1800 grams.

Paulownia is hard wood, bamboo is grass. Bamboo is heavy almost as alu (again, alu which grade?).

Bamboo composition float, alu is from 2700kg / m3

Sure, and?

alu mast is hollow

Light and Frost has made 10 masts to date from 50cm to 90cm and from straight to curved.

We use 3cm plywood and then glass over the plywood shape. The center of the mast provides very little strength. You also do not need to use carbon fiber. We do not like mono structures like carbon fiber(CF) due to impact resonance damage that occurs. If we use CF we prefer to embed it in fiberglass wrap and epoxy mixes like silica powder or micro-ballons.

I haven't done one yet but I'd favour a synthetic core like Gurit M foam because it can be both lighter and stronger in compression than paulownia with grain running length ways. And trying to shape end grain paulownia... not going there! Maybe if I'd built a CNC machine but not yet.
And then lots of unidirectional alternating with oversized and tensioned sleeve composites.