The STN1110 developers were saying they could develop the functionality, but that has died out and they have closed my support ticket.
Im thinking this interface now:
http://www.mictronics.de/projects/j1850-vpw-interface/
GPL firmware source code is in the firmware zip and the TX message size limit is present but it doesnt look like there is any reason why it cant be expanded to use whatever ram is available. It probably would be possible to compile the firmware for an atmel with more resources too. I probably wont have time to look in to this until next year, though. Anyone wanna build up a small run of these?
I'll attach the pdf and the zip here incase the original site dissapears. Thanks to Michael Wolf for creating this board and firmware and especially for releasing under an open source license!
If you decide to use this, check the above site for more information and possibly newer releases.