on a whim, i bought some air soft pellets one time [only $4.99 at wally world for a giant size bottle of pellets] and tried them inside some tires on my "bus" [caravan].
i measured the amount for each tire on a postal scale, installed one side of the tire on the rim, dumped the pellets in, then installed the other side of the tire.
they seemed to work. as these tires and wheels were my winter tires, i used them for several seasons and all seemed ok. as last year was a virtual no snow winter, [] i didn't put them on.
would i do it again ? i really don't know.
just my own personal experiment. your mileage will vary.