anyone can correct me if i am wrong but i believe if you have a cash account and you are trading with unsettled funds and do it more then a certain amount of times then they restrict your account because you don't have a margin account. and they can't charge you for using borrowed money so they slap the restriction on you or give you the option to open a margin account. i think any account you have will do that its industry standard. sec rules and regs i think.
there will be no restriction with Zecco as your funds to puchase new stock won't be accessible until it is valid to sell. Works a lot better with Zecco, there systems keeps it in check