Required 5-Year Rubber Component Replacement ???

Those fancy fuel hoses came with my kit.  I'm not planning to replace them  ?

"The 17MM hose that Rotax uses is not Gates. I've talked to the MFG. 17MM hose is made and used in the European market. There is no US equivalent so just use the 17MM hose. US standards are either too small or too large."

OK, but that 17mm hose on offer in the UK is Gates hose.

You do not say who "the MFG" is, but is there any reason not to use Gates hose if it's the correct size?

Rotax would like you to use their 17mm hose. For liability I would. That said the other 17mm coolant hose should work, but I have never tried it, but I'm aware of that hose.

As a mechanic and owner I'm always concerned about litigation if something ever happens. I spent 28 years going to court and it's best to stay away even if you win. You would have to explain yourself with no way to back up anything up to the FAA, Insurance company and in court if sued by another party whether in or out of the aircraft from an incident.

Fair enough, re liability. But, of course, you, as a professional aircraft mechanic and an official Rotax IRC, sort of have to use the official product. I am sure you have a lot more to worry about, in terms of liability, than some guy with a repairman certificate working on his own E-AB.

Food for thought:

On the liability aspect. If you carry a passenger you're liable, if you crash into something on the ground you're liable and if you have insurance it may be negated.

Usually the term  "best practices" and "tried and true methods" may be adisable. Many Rotax owners have caused major damage and had accidents because they thought they knew more than Rotax, but have not done any scientific research testing before doing non Rotax practices.

For a few dollars more here an there worth the risk???

Just food for thought. 

Is it really worth it in the end????

Working the streets for 30 years I always heard "well that never happened before". My reply was "until it did". :) 

I get your point, but in the case of an experimental amateur built, ANYthing the builder has done could be seized upon as his fault.  The mere brand of tubing, if of a similar and proper type to what the manufacturer (may have) originally supplied, seems hard to argue against.  Indeed, in the Rotax installation manuals, they specify types of hoses, but do not specify brands or suppliers.