They have been working great for me. Ron has done two of them for me, I never felt a bit unsafe using them. What do you think?
Here is the post from MM

I bought a used White a couple months ago and the breech plugs flash hole was at least twice as big as what they are when new. The White breech plugs are one piece with the #11 nipple. I think that nipple would last my lifetime but once that flashhole gets too big you get a ton more blowback and I think the accuracy suffers.I had bought some new breech plugs but I had an idea that a ventliner ought to work in there. I sent it out to Ron Laughlin and he did an excellent job drilling it and tapping it for a ventliner.
I finally took the time to try it out today. I shot 13 shots using Remington #11 caps and Triple 7 fffg. Ignition was flawless. I do think the blowback was less than I was getting with a new breechplug. It will be interesting to see how many shots I get out of a ventliner before the hole errodes too much but it is cheaper and easier buying ventliners than new breechplugs.
I can't think of a downside to making this conversion.
Art
This is what the breech plug looks like with the ventliner installed

Ron could tell you much better than I what he did to get the plug ready to accept the ventliner. I think it ammounts to machining the plug so the head of the ventliner will seat tightly and drilling and tapping a hole to accept the threads of the ventliner, I think they are 10-32 but I'm not positive.
Here is the plug before installing the ventliner

Here is kind of a blurry picture of the ventliner
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Hope this helps
Art