Cage trapping in the west of course is a result of the loss/restrictions of foot holds. AZ was first in '94 followed by Colorado in '96 CA '98 and WA state in 2000. Of the four CO is where I have seen the greatest use of double doors likely because those mountain cats can be so hard to get into a cage. I have never had much problems getting cats to enter cages in the deserts of AZ and CA. I figure around 70 percent captures/visits. In Colorado the same techniques can sometimes cause you to pull your hair out.
Colorado was the first place I ever heard of double door cages and multiple guys building them and offering for sale. Never have run across anybody in CA or AZ and only a couple of guys in WA. I'm fairly ignorant as to Washington. Might be more prevelant.
It was about six years ago when I got to see double doors in action for the first time in North West Colorado with a guy named George Bosik. He has a few You Tubes if your interested. Search "thinkinthebox". I believe he used to post on here. We caught two the day I checked with him. His system was to set under the ledges on S facing ridges to avoid the heavy snow in that part of the state. He uses large amounts of lure. He didn't mess around with four ounce jars - those would only last half a dozen sets. He would put a big glob under the pan then set the trap over it and brush it in to the point the cat could only go way around, leave or go thru. He also believed in call lure above the set and had some long range call techniques. The cage traps he had engineered, built and sold were truly unique and impressive given his limited fab facilities. I quickly got him hooked on my Lead In scent and he started using it in all his sets. As I recall he told me he had only ever tried to catch cats in single doors his first season with little luck. He has caught quite a few in DDs.
Other DD guys I have talked to prefer to set them in a tight trail and either do nothing or just dowse them inside with bobcat urine.
I myself have caught a dozen or so so far in my experimenting and I always have used lure, urine and hanging bait. I throw the sink at them.
I published a DD bobcat catch on trail cam 6-7 years ago. cagingbobcats@l.com on You Tube.
So far my trail cam work and testimonials from friends indicates that bobcats react to them just like any other cage. They first smell it and investigate real good. The thought that they encounter it and just walk through just because does not add up in my head.
Being able to see through should add up to being more likely to enter. Jury is still out IMO.
ML