> The following are the sizes of the marshal data:

Can you please measure the time of unmarshalling? It would be interesting. If you can count the statistics about marshalled types (what percent of shared and non shared integers, strings, etc), it would also be very interesting.

> There is no reason _not_ to reuse INT objects if we are doing it for other immutables to.

There is at least one reason. This increases size of the refs table.