Well... with me being a Fender man.... I can't say that I know what it's like to practice for 4 hours with an overpriced peice of mahogany strapped to me... haha... But seriously, Les Pauls are known for their weight problem... In most cases, the back pains occur when the player has the strap set so the guitar hang too low... Causing the player to have to bend slightly to play comfortably... A good tip for all guitar players is to adjust the strap of the guitar so it hangs at a position that you can stand up right and still play comfortably.... Try not to hang your guitar reaaally low... I know it looks cooler... Back pain > looking cool.... atleast in my book.

A Squire Strat isn't a bad guitar... I wouldn't recommend going with a lower end Squire though... If you're looking to go up... I would look at one of their solid Alder body guitars... rather than one of their cheap ones made of plywood... It will give you a good platform to work with and a decent price. The higer end Squires are around 170 dollars or so.