we work out of Porthmadog every month. Launching on the slipway in town. We are working for the Environment Agency when there so are assisted with parking space etc by the harbourmaster /use their premises.
The slip has a pretty shallow slope at the bottom /when the tide is low.....easier to drive onto the trailer when there is more water...an hour each side of tide is good.
My suggestion would be to give the new harbourmaster (David) a call and have a chat re your requirements /options etc. He is a helpful guy 01766 512927