The old, immediate post WWII mixtures of petrol and alcohol were preferred to straight 'pool' petrol and personaly I am not worried about the "performance" aspects of the brew!

However, the solvent effects of ethanol on paintwork and glass fibre are well known, it also digests many of the rubber/plastic fuel fittings that were fitted as "standard" until recently, so this is where my main concern is. Fuel lines on my Yamaha SRX' are buried beneath the fuel tank, directly above a hot cylinder and exhaust silencer beneath! Annual checks and replacement with 'Viton' fuel lines and quality fuel filters appears to be the answer. Carb and fuel pump diaphrams not made from 'Viton' are likely to prove more perishable!

Powder coating appears more resistant to the solvent effects of the E10 fuel and I intend to use that painting method, rather than liquid spraying on future projects. A powder coat can be flatted back and oversprayed, with a liquid paint that can then be given 5 or 6 coats of lacquer to finish, if required.
Nigel Lacey and I have also had a blether about fuel additives to prevent condensation/fuel separation and I have been using Castrol 'Valvemaster', as it not only requires 1ml to 1litre of fuel, but also prevents valve seat erosion, so two birds, with one stone in the case of the '74 450 MKIII.
I have filled up the Yamaha SRX600, a Honda Bros400 and the 450 MKIII, with E10 and then added the appropriate amount of Castrol 'Valvemaster' and have not found any deterioration in engine performance, or separation of the fuel. At present the machines are doing at least 50 miles a week each.
Three bottles (750ml) of 'Valvemaster' for £33-00 delivered from a UK eBay seller seemed fair enough to me.

If a bike is going to be off the road for any longer than 6 - 8 weeks, then I shall drain everything down and put a mist of 'Redex' and or 'Bulldog BDX' to the internal surfaces of steel tanks.
I too, am sceptical about the claims made for the potential catalytic, metallic shapes. I have never seen the seller produce a double blind, positive test result from the use of his 'product'.
Good health, Bill