SF7 Flash Sync Speed

I have just bought a SF7 body off eBay to replace my dead Chinon CE-4, and am very happy with the way it can use all my manual focus lenses. I also have an auto flash unit (not Pentax dedicated) which I guess I should be able to use OK. When used on the Chinon I had to set the speed to 1/60. The SF7 manual says a dedicated flash would automatically set the speed to 1/100, yet the closest I can set manually is 1/125.

Can anyone tell me what would be the best speed to use when using my flash unit?

Thanks.

Anything slower than 1/100 then
Obviously, if you go really slow, then use a tripod as well as the flash (this will enable you to balance the available light with flash light)
Matt

Thanks for that! Think I'm all ready to go now