Keith,

I am perplexed, by "flax" do mean flat?  (Quite a stretch for a typo, but
I've done it.)  Do you mean gold or OSP?  (Being of yellowish color.)
In either case there won't be a problem.  Potentially some heart burn, but
that will be for your assembly folks.  For example, with OSP, Silver, Tin
(and really all finishes) handling is very important.  Fingerprints will
cause solder joint problems.  Workmanship issues as such I assume are not
your problem.  Gold finish seems to the topic lately.  A non solderable
condition called "Black Pad" just is the things nightmares are made of.  It
is a lose/lose condition.  Personally I like Tin.  I recommend Silver because
it is more accepted (many folks feel tin is four letter word).
In any case, I suggest you search the archives here.  I strongly recommend a
coffee and a "do not disturb" sign on the door as there is a lot of info on
the subject.
Make certain you confer with the folks that fab and/or assemble your product.
 But whatever you do, keep your fingers OFF the board... (man, I'll never do
that again).

Good luck and let us know what you decided,

Boston Brad
781 858 0783

Brad Saunders
Field Applications Engineer
www.coretec-inc.com
PCB Fabricator