You need to use change-at-point. 1) First create the lathe finish operation. 2) In the "Operations Manager" click on the operation's "Geometry". 3) In the "Chain Manager" right click on the chain. 4) In the right click menu select "Change at point". 5) Select a point on the chain in front of the point that you want the feed rate to change at. 6) In the change at point dialog you can change the feed rate and other things like the spindle speed. 7) Select Ok, <ESC>, Ok and regen the lathe finish operation. The new feed rate is now stored with the chain so you get the new feed rate when you regen the operation. The feed rate will change on the selected move only, which is useful for slowing down in corners.

Actually there have been some improvements to Mastercam Lathe. This is from the "Whats New" pdf. X4 1) Groove supports multiple chains. 2) Groove finish has an option to overlap in the middle of the groove. 3) Groove finish has optional separate feed rate and spindle speed. 4) Groove finish has optional dwell in corners. 5) Groove rough has optional first plunge feed rate. 6) Groove supports tool inspection. 7) Improved ability to create a turn profile from a solid. 8) Verify has improved support for boring bars. X5 1) New plunge turn toolpath, based on the Iscar plunge and turn tools. 2) Chuck unclamp has an option to eject the stock. 3) Cutoff can start the cut at an incremental distance from the stock, instead of an absolute height. 4) Cutoff supports back face stock amount, to leave extra stock on the cutoff piece. 5) Cutoff supports an optional secondary feed rate and spindle speed, at a defined radius. 6) Cutoff can optionally keep both halves of the stock, instead of just one half. 7) Rough supports tool inspection. 8) Rough has an extra exit amount, to extend the end of the cut. 9) Rough has an optional front clearance angle. 10) Lathe toolpaths support cutter comp in control optimization, to remove small internal arcs. 11) Improved lathe tool compensation. X6 1) Improved cutoff/pickoff operations, requires post processor support. 2) Rough supports variable depth roughing. 3) Rough has a remaining stock option, to minimize air cuts. 4) Finish supports downward cutting, which breaks the chain into sections and cuts the sections individually. 5) Finish supports tool inspection. 6) Improved canned rough and canned finish. 7) Canned groove has optional separate feed rate and spindle speed for finish passes. 8) Face toolpath has optional separate feed rate and spindle speed for finish passes. 9) Face toolpath has optional corner break, for radius or chamfer, and various cutting strategies. 10) Groove rough has optional first plunge retract feed rate. 11) Groove finish has an option to remove undercuts from the chain.

You can create your own tool by selecting the insert from an insert catalog and the holder from a holder catalog. The insert, VNMG 332, is in the inch insert catalog, LATHE_INCH.LIC. The holder, MVJNL 2020K 16, is in the metric holder catalog, LATHE_MM.LHC. And you can combine inch and metric lathe inserts and lathe holders. The software will automatically scale to the current system units.