Can a HMS Bey Stadium be used for plastic bey battles...?
Or it's not recommended?

Thanks.

you can, some ppl actually do it cuz the exit holes are smaller.

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"Twilight stands for the dawn and the dusk. Where do you stand?"

but doesn't it penalizes some types (like defense type)?

You could have posted in:
http://forums.beywiki.com/showthread.php?tid=1295

Beyblades usually go in a circle. The HMS Stadiums are built in a small oval.
This stadium doesn't give advantages to any type, only disadvantages.