Is correct cleat positioning simply what feels 'right'?

I found this absolutely perfect for me and a friend:

https://www.competitivecyclist.com/Store/catalog/fitCalculatorBike.jsp

For a start, it recognises that there are different styles of fit for different folks.

Just follow the calculator and then see if you're close.

To give a counter-point, I had a bike fit after experiencing some knee pain once I started riding more often and longer.

After £450 on parts + the cost of the fit; I found it made things even worse.

I then did a load of research (Steve Hogg has a ton of info on his site which worked well for me) and spent a weekend riding making lots of minor adjustments via trial and error; and have been pretty much pain free since.

You can do it yourself.

+1 for a bike fit.

Had one last year as I couldn't get sufficiently comfortable on my new bike. Best money I spent. Apart from saddle and stem changes, was recommended some insoles for my shoes, which made a difference even though I had correct cleat positions.

I had a bike fit for £50 the other week. He changed my cleats - they were OK before but now they're even better.
If you live anywhere near Worksop it's worth doing a search for Andy Bishop bike performance. Reasonable cost and the he was recommended by word of mouth by a local proper roadie. Well impressed.
I have no affiliation just a happy customer and seems a few travel quite a way for a fit. It's an option perhaps.

Don't hear anyone, make a fit. Is the only right way. Think how much pain, money and bike hours you will lose if something go wrong. 

I would definately advocate a bike fit No offence intended but there is some spectacularly bad advice being given out on the internet about where to put your cleats your saddle etc.

You can have a basic bike fit done for £100 which is what the price of a lunch out? it's nothing in comparison to, at best a lot of time wasted, at worst giving yourself a potential injury.

It take a couple of hours and if they're reputable then you should be able to go back and get a second consultation to see how you are getting on with the fit.

I tried siting my SPD cleats so that they're as far back as they can go, with the aim of adopting a midfoot pedaling position. It just felt so strange. Wasn't comfortable for me personally, so I went and adopted the more traditional "ball of foot over pedal spindle" placement.

I understand going midfoot with cleats has more potential benefits for MTB riders, especially downhill riders, since they're all about maintaining pressure "behind" the pedals instead of "on" them for riding security purposes. Most of my riding is on the road though, so it didn't apply to me so much.

Need a set back cleat position? Check:
http://www.ebay.co.uk/itm/-/152455458004?

Have you had any problems with your SPD pedals/shoes?

Having fitted quite a lot of non-athlete people to  bikes (as well as a few athletes), the efficiency of power transfer is a tiny minor percentage once you get your saddle position close, and in my experience injury prevention and comfort come before other considerations when it comes to cleat position. Comfort and injury prevention seem to go hand in hand (or cleat in shoe). So, unless you are Alex Dowsett looking to knock another 3 sec off yr TT record, then go for comfortable.

If your only concern is avoiding injury then I guess if it feels right it must be right.  But if you are also looking for maximum power transfer and ease of clipping in/out you would do well to follow one of the YouTube videos on the subject.  Try several.

Are you sure it's not the newness of the SLRs that's putting you off?  They do feel a little softer and more vague than SPDs.

In fitting the new cleats you haven't disturbed the inner shoe in some way?

Keep going!