I did some Finite Element on my Tower. I had 4mm 'banana' plates and 3mm everywhere else.
Basically the tower will withstand a bog load if it was hit vertically, but that, as has been discussed before, it is not a good thing because the rider will sustain the damages. So, AntiPaul's excellent design will absorb the energy and break on impact.
You have seen in the previous messages that PE is a good material. If your run FEA with PE you will laugh your heart out
. So, FEA is not of major help here, as the tower, under normal conditions will hold what? 2? 3 kg ? Something like that.
As far as the side blows is concerned, there is no design at the moment that will hold the dynamic impact from a crashing bike. I am quite busy designing a roadbook holder these days, but at the end I would like to create a tower what will protect the equipment from falling apart. A damaged roadbook is of no use even if the tower is straight ...
You cannot make the equipment strong enough to withstand a direct hit, so you can make a tower which (1) will retract if it gets hit by the rider and (2) it will divert the forces somewhere else if it gets hit in order to protect the nav equipment. It can be done but it needs time designing which I do not have at the moment