I dont think the position size or account size would have something to do with the pro vs non pro classification. At least it has not for us so far. Normally it would have to do with employment, registration with NFA / SEC and if the account is set up as an entity and not as an individual/joint account ( and even then that is not a sole criteria). So the answer is the position size or the account size would not set off classification as pro. Be happy to answer specifics via PM if you like.
Commercial banks & traders do it constantly, some to hide their larger lots by scaling in & out of positions. If you account is on the phatt end any brokerage firm will let you trade wit da big boys...good luck.