The misfire I will guess was due to the length of time you left the rifle charged with Triple Se7en and not the #11 cap ignition system. Changing the ignition system is again a choice only you can make. 209 primers will give you more fire into the channel and also more headaches expecially if your shooting Triple Se7en.

Did you have hard crud rings when shoot T-7 and #11 ignition? I personally never experienced them. You might very well experience them with T-7 and a 209 ignition system. I guess there are good and bad points for both sides. Check with Knight and make sure you do not have to change out the striker system too. Just a new breech plug and nipple is rather inexpensive to replace.

I have a Wolverine II with the #11 caps ignition. Great shooting, fun to shoot, easy to take care of rifle. Would I change over to the 209? Nope. If it ain't broke, no need to fix it. You of course (and I understand the ease of the 209 ignition) might see this different.