Blade tip speed should be the same as with other blades because that engine should have a max. rpm setting of about 3600 loaded (with blades engaged)or unloaded. That is one function of the governor on these engines with carbs is to get the engine to max rpms under load and to help keep it operating at that rpm whenever possible. If you put a tachometer on the engine and check the rpms (not a bad idea anyway to make sure it is running at the 3600 rpm setting) unloaded and then after you engage the blades, you should see the engine have a short drop off in rpm's and then it should gain back the rpms back to within 50 rpms of original reading, if the governor is set properly. With the bagger going, I'm not sure if the governor will be able to compensate for that much extra rotational mass being turned.