Right now our options are:
1. Send the whole frame for heat treatment after welding. But that
costs a huge crapload of tamales. and our budget is a pitiful
$1500.
2. Change to steel. Steel has an even temper (pardon the pun
) that does not change with welding. The techs claim
that we can compensate for the extra density by making the tubes
thinner by 1/3.
The problem is that stainless steel is tough to weld, and mild
steel is prone to corrosion. And besides, mild steel tubes of such
thinness are hard to come by commercially in Singapore - we'd have
to import it.
3. Either increase the thickness or the outer diameters of the
aluminium tubes that we're using.
Looks like (3) is the only viable option right now. 
