It's a little dicey using aluminum. You would be soldering a copper based lead in - presumably the center conductor of a length of coax - to aluminum; the dissemilar metals will eventually cause a chemical reaction that would cause problems. There are chemicals, as I understand it, that will allow you to solder and bond copper to aluminum without problems but to be honest I've never had the occasion to use them.
We should also be careful about using the term 'longwire'. A true longwire, such as a Beverage or Vee-beam, are a wavelength or more long, and in the case of the Beverage, can be terminated at the far end with a resistor to make them more uni-directional (the Beverage is bi-directional, more or less right off its ends). What most folks put up are better termed 'random wires' or 'inverted L'; the latter being a length of wire with a lead in coming off the nearest end to the house.
The Vee beam was discussed extensively in books by Bill Orr W6SAI. In them, he describes them as each leg being a wavelength or more long, and fed with ladder line.
All three have their place, just be sure to be clear with the terminology. 73 Mike