The only reason I saw a stick rejected was because it was too slow - especially in access time. You have to measure your stick and your disk and compare the numbers. If the access time of the stick is way over 1ms, it will not buy you much as the data transfer rate is probably many times slower than that of the disk. HD Tune
is what I use for measurements. But let it run until it stoips, else you will not get the access time.
But in general, as Deacon Frost says, you will have little measurable effect with ready boost.