Gentlemen
If you are arriving on a charter flight into Puerto Plata, the customs doors open and everyone walks out with their bags UNLESS it is in a cardboard box which the customs must open by law, HOWEVER, if you arrive on a regular flight then you have a chance of your bags being opened, but a lot of the times there is a charter flight at the same time and if you are a gringo (non-dominican) you can also walk out the 'visitors' charter flight door. Wearing tourist clothes helps and most 'gringos' I know have brought in many items as long as it fits in a suitcase. A rolling hardsided one is best for packing stereos/computers and such. You can enter 5 or 10 times without ever having your bag searched. I am not sure about landing in SAnto Domingo, it is a much more chaotic entry.