I just took a fmq class from Sue Nickels and she doesn't recommend going very fast either. She says just go at a speed that you feel comfortable with. She's an excellent teacher by the way. I do know that you should practice A LOT and that will give you more control over hand and foot speed when you do your actual fmq. I'm also taking a fmq class at my local Bernina dealer to learn to use my Bernina Stitch Regulator. I don't know if I will prefer using that or just the regular fmq without that special option.
Verna in So Cal.