Nah, there's other ways.
I used one of which made me only loose 3 lives (energy tanks) against the boss
Shortly, lure the sa-x to the ground (the main point is to make it not use the screw attack on you). Remember to charge your beam all the time. Shoot the sa-x when it comes to the ground.
It will then try to screw attack into you (as a security precaution, i suppose, otherwise it'd be just too easy). He'll go vertically or horitorzonolly (really, i don't see how it can do the vertical one, though, 'cuz you can't do it, neither in this game nor the previous? lol).
Anyway, if he jumps vertically, jumps over it and shoot it. If it jumps the horitozonal way, run under it. Then shoot it.
If it would summersault into you, don't jump away; RUN away while your invicibility lasts. And as for a last advice, you can screw attack through his shots. Don't go too far up or away from it, though, or it'll chase you around using the screw attack; and you can't get away from it, 'cuz it's faster than you.
Piece a cake if you do it right, really. Otherwise just try to get all the e-tanks.
Btw cooliscool, you cheater
that's cheating, no doubt!
Nice pic, though, heh.