Hose clamps work OK
I can only burned at the stake once so I might as well..
In my old Zenair Zodiac I had hose clamps everywhere..not one of them ever failed in 500 hours and the new oners have not reported any problems..The Yaks from Russia are also covered in hose clamps..They work Ok but they are not as bullet proof as what we normally use.
I would not use them for high pressure but up to 10psi I am comfortable with them.
Here is what i would do..You have a 1/4 or 3/8ths piece of tube coming out of the header tank right?
Go to the hardware store and buy a copper compression fitting of the same size.
Slip the cap end over the tube towards the tank and tighten the fitting.
remove the fitting and the compression ring is still firmly attached to the tube.
Now take a Dremel or whatever and cut the cap lengthwise so you can remove it without damaging the tube or tank...quite easy.
Slip the rubber hose (yes from your autoparts store) onto the tube and over the compression fitting...Use a hose clamp in the tank side of the compression ring.
The tube will never pull off because the hose clamp won't slide over the bump that is the compression ring.
Use firesleeve over the rubber hose and hose clamp.
There you go a very solid connection...And of course someone will start whining about how the copper ring and the alu tube are not compatible..well use a little grease and it will be air tight. I used this method for 500 hours and they all looked perfect at every annual.
Frank