>>42717646I did the math and i'm wrong.
Assuming the physics are somewhat realistic, mass = vol*density.
Now, smaller pokemon are increased in size more than the pokemon that are already large. From the trailers, D-max Gyarados and Raichu are the same size, so. The lightest pokemon is a big tie, but the tallest is haunter at 5'03 or 1.6m
D-Max Riachu as per pic related, is about 10 gloria's tall so we'll say 15m which is about a 9.6x multiplier.
Overall the formula is
m2=((h2/h1)^3)*m1
Where 1 is base and 2 is D-max. Of course, this math is simplified, doesn't use exact measurements, is based on a lot of assumptions and was only done for shits and gigs but it's sound under its own logic.
A Dynamax'd haunter would only be 82kg, gastly at 150kg.
Granted, they are immune/resist both of those moves so i think it balances itself out. Though, your specific example drifblim, is 30 tons and has the same stipulation