Dosage for Robaxin - 2 a day?

My pain doc prescribed Robaxin 500mg twice a day.  It's about like taking 1 Tylenol, which is barely noticeable. 

At first I had some minor side effects, but they're gone now.  I looked up the dosage and it seems I'm taking 1/4 the minimum maintenance dosage - which would seem to explain why I am getting next to no benefit.

Should I ask my pain doc to increase my dosage to see if it will be helpful?

I am currently also taking Vicodin, but would like to reduce it, or preferably find something else to replace it, as I am getting tolerant.  It helps with fibro and arthritis pain, but a muscle relaxant helps also.  I tried Flexeril, but it put me to sleep. 

Straydog -
I guess Robaxin wasn't effective for you, or maybe you weren't prescribed an effective dose either. Does Zanaflex make you sleepy?

I need a muscle relaxant (or else just a more potent pain med) because I get back muscle spasms and the fibro pain that seems to trigger tightening of muscles also. I've had several injuries to my back, resulting in bad arthritis, scoliosis, radiculopathy, etc., and I find it locking up when I do anything resembling work - like taping off and painting a wall today. Ouchies! I'm hoping it does something for my sore shoulder tendons too. I can't lie around on a heating pad ALL day!