The quad rings would work very well I would say, but the "O" rings can't be beaten for simplicity, and there is little actual pressure pushing on them. One thing to remember when trying out different forms of seal is that you need to allow for the change in angle of the tube as it enters the crank case, so adding extra inserts, or any other hard lip type seal is highly likely to suffer some damage unless the bottom of the tube has a generous radius and some form of lubricant to help it enter the seal. It would deform quite a bit before the tube settles as the head/ barrel reach their seated position. I had this issue a few years back when assembling an RTV engine using the original type seals, and the tubes guillotined off a piece of the seal due to the angle of the tubes. This turned out to be a misalignment issue of the holes in the cases verses the tube angles.