if i rest my forearm i cant reach the higher strings but if i elevate it its easier to pick and better control but the problem is that guitar neck moves backward and already tried both sitting positions. How do you guys do it? Ive seen videos from players like john p. And jeff loomis and the guitar stays in place :/
If you watch Jeff Loomis play when he's sitting down, you'll notice that his right forearm is just lightly resting on the guitar body and moves downward as he picks from lower to higher strings.
If you rest your forearm with a little less pressure, you will be able to let it move down to reach the higher strings but still retain contact thus preventing the problem of the "floating" neck.
For most electric guitar playing my palm heel is most important - and like Tim, I rest it near the bridge, but typically my rest position is with a very light touch.
When sitting, my forearm does touch the guitar, but even more lightly. When standing it often doesn't touch at all.
This works for all my techniques from arpeggiated picking, sweep picking and alternate picking, and the only times I really move away from this is when thrashing out rhythm chords, where I might just move my arm in all sorts of ways :-)
Unless you're strumming, the picking hand is best placed so your palm, where it meets your wrist, is just behind the bridge. If you want the sound to be more nasal, move the hand to the right, so the pick is closer to the saddles. If you want to palm-mute, move slightly to the left. To go from bottom to top string, slide the whole hand vertically. Your forearm will probably rest gently on the guitar body, behind the bridge.
Wearing a strap, even when seated, isn't a bad move.