Hey, I spike cocos palms that's all.
Personally I reckon the spikes should have a hollow centre and be pressurized with round-up so as I go up I give them a good dose.
But I read some stuff on guys spiking other trees and the spikes only gauge the bark, bark is very thick.
Today I had my longest gaffs on and tried to spike up the bottom 2m of this big azzed paperbark ... couldn't get to the wood, was like 4" of flaking papery crap (zero grip) and had to get my line up high and air hump to some branches. But it was a TD.
I'm sure dudes spike those Doug firs all the time.