I am trying to fix a bug in sitebricks where it consumes the input stream in of the data of all servlets even those not using site bricks.
HiddenMethodFilter.java line:66
String methodName = httpRequest.getParameter(this.hiddenFieldName);
See http://code.google.com/p/google-sitebricks/issues/detail?id=45
Yes you can provide your own request, see Modify request parameter with servlet filter.
Furthermore may be extending the wrong sitebricks filter might be easier than chaining.