So I decided to try constructing bait feeding stations and have been pleased with the results. Here is one of them.
They are made of 1 1/4" ABS pipe cut in 8" lengths and you need 3 pieces for each station. You will also need a T fitting of the same size and a 1 1/4" plumbing test cap or perhaps a large cork would be cheaper if you can find it. I have trouble getting the caps off to refill the centre pipe with bait. The main thing is to keep the bait dry so the cap needs to do the job well. We used ABS cement to fasten into the T fitting. To set up, just tie it to a stake, making sure the base is in contact with the ground and level so rain won't collect inside.
As for spacing of the stations, I set up one every 15 feet or so because there was so much evidence of rodent activity. They should probably be put out in autumn to discourage the usual search for good nesting sites for the winter, so you have a few months to get the stations made up and ready for use. There are several good commercial baits available, I used a single feeding anti-coagulant rodenticide called Wilsarin, put out by Wilson. Their active ingredient is called bromadiolone and it seems to be working just fine although the grain type might resist moisture better.
I took off the geotextile and will mulch with straw as usual over the summer and consider removing it after the leaves have dropped. I was replacing the mulch each spring anyway to resolve a fungus problem.