I'd imagine that is a complicated overflight is in Canadian airspace but with an agreement on use for overflight. It's been a while since I did it, but I recall coordinating with KIAG tower and then self announcing on the Unicom before returning.
I wonder if you could file a flight to IAG and then one out and pick up your new clearance in the air after the falls tour?
It's really not a problem - well established sightseeing routes. Contact KIAG, request the sightseeing route, and they'll give you info on coordinating with the Canadian controllers. I flew it out of KBUF but the procedures are the same. Details are in FAR 93.71 & 93.81. NavCanada has details and a great map (which makes it really easy compared to the US description) at
Just ask...today on the way home I asked..."Request heading of 260 for a bit to avoid a layer up ahead"...controller came back with..."deviation as needed approved...let me know when you are back direct Salinas"...easy peasy and gave me more leeway than I was expecting cuz he knew the "why" with the request.
Also while IFR training we did just what you are asking...got IFR above a layer, did a bunch of maneuvers VFR then IFR back once we were ready to proceeded. Just told the controller what we wanted to do and he worked it out knowing our intentions.
Now, don't suck up air time with what your lunch plans are, but plain ol english concisely can get ya a lot vs trying to formulate some official sounding request that will keep the controller guessing as to what your intentions are.
Is the weather an issue to the point that you can't make the flight VFR? It might be easier to just do that and take a lap or two around the area as you pass by. That's how I'd personally do it.
Otherwise, as has already been mentioned you could just ask the controller in plain English what you want to do. They may let you or they may not. An alternative might be to cancel IFR, do your sightseeing, then pick up a new clearance and motor on.
I was departing Niagra in the Pilatus and I told the controller my pax wanted to see the falls so I was going to depart VFR and then pick up my IFR in the air. He told me no need, departed IFR, given vectors to the falls, a clearance to circle a couple times and then on course.
The US VFR Chart Supplement has the same information. If you are IFR, I presume that ATC will ask that you cancel IFR "advise when ready to cancel" and then you fly the route VFR and when checking back in with ATC when you are ready to resume your IFR flight.
I did the same thing from VFR flight following years ago, they cleared me off freq when flying the route so I could make the required calls and then picked up flight following coming out the other side. They did let me keep the squawk.
The big thing is to make advisory calls on the air-to-air frequency (122.050), never be below 3500', speed at/below 130 KTS or minimum safe speed, etc. The air tour operators inside CYR 518 will report perceived violations to Transport Canada. The Canada Flight Supplement NIAGARA FALLS VFR TERMINAL PROCEDURES CHART (available though fltplan.com > Documents > "CFS ON VFR Terminal Procedures Eff mm/dd/yyyy") has relevant summary info.
Ask for a right or left 360? I got cleared for one on a leader vor/DME arc into a vor approach on an IFR for spacing. We were VMC at that point but still not an issue.