Truncate RSS feed output

Hello, is there a way to truncate or limit to a certain amount of words or characters (a short intro) of posts on the forum?

I am having them imported onto another site, but the site will pull the entire entry, I don't have any options there to truncate.

Any ideas?

I think the old IPBOARD 3 had some settings to control the RSS export but I can't find anything in IPBOARD 4.