Midlife, from the AIM:
4-4-7. IFR Clearance VFR-on-top
a. A pilot on an IFR flight plan operating in VFR weather conditions, may request VFR-on-top in lieu of an assigned altitude. This permits a pilot to select an altitude or flight level of their choice (subject to any ATC restrictions.)
b. Pilots desiring to climb through a cloud, haze, smoke, or other meteorological formation and then either cancel their IFR flight plan or operate VFR-on-top may request a climb to VFR-on-top. The ATC authorization shall contain either a top report or a statement that no top report is available, and a request to report reaching VFR-on-top. Additionally, the ATC authorization may contain a clearance limit, routing and an alternative clearance if VFR-on-top is not reached by a specified altitude.
section b. there is quite common, and as mentioned, if IFR is cancelled, then you are totally VFR. Controllers in my area certainly understand this, and will give an "report of not on top by xxxx' (it is usually 4000' in my area)". Cancel once you are 1000' above the layer, and the VFR-on-top rules no longer apply, since the IFR is gone from your flyin'. Then, if needed later, a popup clearance for an approach to get back in. On busy days, there may be a 10min delay or so for a popup departure, or approach, but that is not typical in my area (unless everyone is out gettin' IFR current