Improving Fitter Routing

Hi...I did change some of the additions using carry ripple adders which I guess is a sort of pipelining. I guess fitting placement is succesful [where the average interconnect usage is 61% and peak interconnect usage is 90% when using placement effort multiplier = 3]. However, I am still getting this error "Info (188005): Design requires adding a large amount of routing delay for some signals to meet hold time requirements, and there is an excessive demand for the available routing resources. The Fitter is reducing the routing delays of some signals to help the routing algorithm converge, but doing so may cause hold time failures. For more information, refer to the "Estimated Delay Added for Hold Timing" section in the Fitter report.". I do not see any such section in the XXX.fit.rpt and I am not sure how to interpret the results to check if something specific can be done to improve hold time requirements..any ideas ?