Firstly, I don't care how smart you are or how vigilant, sooner or later you'll have a tenax fastener snap as they just weaken with vibration imparted by the closed hood in the wind flow. My current car seems to have the type that fail at the thin stem leaving the shallow install hex still on the surface of the panel which is easily removed using a six point or hex socket. Having replaced them in older cars which seem to fail at the thread section flush with the panel leaving the fractured wood screw end just below the surface. Now I'm an engineer and have had very mixed results with trying to drill them out.. It seems they are distorted in the wood either at the time of installation or at the point of fracture. When anyone presents me with their car with this issue I make sure the old stud is at or below surface level, also you often have to use a body planishing hammer to flatten a lifted edge of the body alloy sheet, then like Sospan I fit the plate type two screw fitting. I first mark the position of the two holes required to be drilled. You have to make sure the fitted plate aligns the stud position with the old one beneath as hood fitting can be compromised. To do this I use masking tape over the old stud hole which extends at least half an inch beyond the plate. I then find the horizontal position I like best and pencil on a line and draw a further line at right angles vertically crossing the old stud hole. This enables you to align the new fitting correctly. Rotate the plate so that the screw holes line on the horizontal line and the stud is at the centre of both lines now mark them. Next I use an auto centre punch to prep for drilling and I use a suitable pilot drill. WARNING don't drill much longer than the screw length..... you might end up drilling through to the inside!

As as Sospan said, if you don't pilot drill the body the screw will shear, in fact don't use too small a pilot drill either. The ash will be fairly hard and that can have the same result! Two further tips here ......... find a hard steel screw and pre-run it in the hole first as this makes it far easier and wax candle the Tenax threads before screwing the screws in. helps lubricate and prevents corrosion. before screwing the plate on I wipe a smear of silicone sealant over the old sheared stud. There have been times when the silicon had gone hard in the tube and I have cut a piece of electrical tape to make a temporary seal then forgotten about it and on replacing again have found the seal to have been totally effective but you make your own choice there!

One last thing. They are cheap so buy half a dozen in order that at the next failure its a simple exchange and at the same time buy the installation key for the female part in the hood material as they too loosen and fall out...... I check mine for security every year!