Both trails have free parking. Sawbench for Marin (Gwydir Mawr) or the hill-parking just off the main road into the Penmachno trail and yes, there’s a donation slot at the bottom of penmach parking since it’s not managed with public funds like the Marin is. If it floats your boat, you can link both up via Gwydir forest, coming into penmachno at the furthest point on loop2 (up a monster, endless fireroad climb), it’s an absolute BEAST of a ride at 90km and 2700m of climbing but a good one. If you do this, it’s recommended to park at the Cae’n y Coed parking on the A5 and start the Marin at The Ugly House taking you onto the new(ish) Dirty Dozen trail. A killer of a start, but it means after 90km, you roll down the hill from Moel Siabod straight to your car and collapse in a heap. There is some awesome off-piste stuff from the Marin down into Betws which is another level of technical, again if that flicks your switch. I’m a regular so will be looking for this cut through to Crafnant and the descent to Capel. Assuming it’s the bridal way on the OS map, starting at Blaen y nant? Anyone confirm? Happy Riding. Both trails are my sanctuaries.