It really isn't a problem catching porcupines, just give them a little time to return. The last time I made blind sets with both 15 and 18 inch wide double door beaver traps with a bit of simple drift fencing, which worked fine, got several in a couple of weeks, no bait or lures as usual.
In response to to those who might be experiencing beaver refusals from other beaver cage traps, I surely can't say why they are having issues. Perhaps narrow traps are part of their problem or bulky, conspicuous door systems? With experience under our belt, we have been trapping beaver almost exclusively with wide, low profile swim through beaver cage traps for nearly 10 years now taking a total of 1,336 beaver with no evidence of refusals of any kind, often cleaning entire colonies of 8 or 10 beaver in two nights without issue. Many ADC trappers have taken 100 beaver per year using these cage traps for many years, racking up catches of 300, 500 and more beaver with no evidence or even a suggestion of refusals. These traps also regularly take both otter, beaver and porcupines, even bobcats, fox and coyotes in dry sets, again minus refusals. With so many variables, identifying real problems and solving them should need not be confused with ginning worries about issues that could easily be attributable to many factors.
You sure wrote it....
As for otter refusals, I have talked with Ronnie .
Talk with Swamprat who I know personally if you want to talk otter. He uses both and prefers the advanced.