buffer size increase

is there a way to increase the buffer size beyond 2048 on osx? i am using a pure data patch that is quite hungry and theres still occasional glitches even at 2048. the menu in ardour shows the options for higher buffer sizes, but the latency won’t increase because jack doesn’t seem to allow it. is there a workaround for this?
high latencies really don’t bother me, but glitches do. the pd patch is cpu optimized as much as possible, but theres a lot of fft and pvoc stuff going on…
any advice is appreciated!

@monas: your audio interface hardware apparently doesn’t support larger sizes. This is not entirely suprising.