I know a guy that works here under a F visa, but his salary is paid in the US. I think the problem will be that with a F visa you will have to leave the country for 24 hours every 2 or 3 months. There are some agencies that can get you a F visa with unlimited stay but be careful and they cost about 5000 rmb.
I worked almost 2 years with an F visa before having a Z ( a real legal one), and, I went out and back to china severals times, but was ok fo me. In fact, There's no problems. If u have money u can buy all the rights u want here... Then, things and prices change every 6 months. I remember just before the olympic the priced doubled. About the visa agencies u have to ask to foreigners in beijing which is ok... Good luck and take care...
Like skaught mentioned, the 2 year experience letter can be nicely forged. However, age is complimentarily a bigger worry since it appears on your passport... if you've pushed 1st jubilee, ignore this concern.
There are just a few good visa agents that convert F to Z in a fairly less complicated process. However, if you decide to play ball with an F, be careful about the following facts:
As Jonathan mentioned, regular visa renewal expenses / exit entry expenses (handled by you)
If company withholds * (owes) * || refuses to pay you say ** months salary, you may NOT get the law on your side to fight for it while not holding a Z visa.
Study the contract terms carefully and insist on some kinda advance payments to keep you on the safe side