At least 2 of the toilet paper type oil filters companies sell there own elements that I assume fit properly and should = no passing around the filter media. If someone is concerned with poor fitting elements they need to buy the ones the maker sells (The one companies is in the $5 each range + the shipping).
Also from the pics I have seen of used TP elements it looks to me like the swell up (some people said they were sometimes not easy to remove ) indicating they hav some ability to fill the filter housing.
In the reading that I have done the biggest complaint about the toilet paper type oil filters is that they need to be changed too often (around every 2500-3000 miles).
I think If the filters are plugging up this means that they must be working.
The next complaint was that they were a inconvenient mess to change. Several people said the got rid of their toilet paper type bypass oil filter system to a spin on due to them plugging too soon or because of the mess to change them.
I have not found any article that said they did not work.

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84 300D, 82 Volvo 244Gl Diesel