I'm running an 88 FXSTC in QLD and wondered if bolting an oil cooler is a good idea, anyone got any experience?

Wouldnt do it any harm bud.

For a quick check, buy a cheap ($10) digital meat thermometer and measure the oil temp after a hot run.
Any hotter than ~110c and it would be worthwhile .
Evo's usually run decent oil temp's without a cooler.

http://www.ebay.com/itm/OIL-COOLER-ANY-EVO-SHOW-POLISHED-BILLET-SPORTSTERS-ALL-1340-CC-ANY-EVO-NO-TOOLS-/222260544854?hash=item33bfc2c556:g:FI4AAOSwymxVLSKG&vxp=mtr

I've used these on my twincams for years , and have fitted them up to all my riding mate's bikes.

They drop the oil temp 20F , SAME as the factory 2007 and up plumbed in oil cooler system

Best bang for the buck by far these are mate

Oil cooler will help with oil temp control

If you install an oil cooler get one with a built in thermostat or if you have one already that does not have this feature ,get a stand alone thermostat and plumb that in , you will be surprised how little the cooler is on line when riding .

Oils used in this environment meets all their test specifications at two test temperatures 40°c and 100°c . Dipping your finger in the tank as a test is not recommended.

The engine in its original construct could handle a very broad range of running conditions without any additional add on's , but a tune/mechanical error or fault can definitely make the engine run hotter, so this would be of benefit to investigate and correct first before adding extra cooling features.

Over the years we have found that some engines even after tuning had a tendency to run hotter in some circumstances compared with the majority of a similar product for no good reason ,the damn things just run that bit hotter .

Goes to show ,not all engines are identically the same in behavior although identical in appearance.

I found that the cooler collars that retroman recommended aren't bad for the cost v benefit

Oil coolers dont do shit if you aren't moving. Better option are cooling fans, i.e Love Jugs etc etc. A combo of both would be best.

Because these slip on coolers work as a heat sink , they do work even when stopped in traffic. Better than the radiator type systems.

AND they're just as efficient at speed , I've conducted a fairly scientific test/comparison on them in Perth traffic on a hot day a few years back.

There was a thread on this way back then

http://www.hdforums.com.au/Default.aspx?tabid=71&forumid=37&postid=476196&view=topic

I am interested to know what the ' hot' is in' degrees' that you guys are measuring or reading off an instrument? and when you have an engine running 20° cooler , what is it cooler than in degrees?
In my previous post i mentioned the use of a thermostat to control temperatures in the oil circuit ,there are reasons for running oil at a given temperature and not too cold ,one being oil behaves as the manufacturer intended , two , cold oil robs power , three ,condensate boils off at operating temperatures . And as i said ,you would be surprised to at how rarely the cooler is full open in the circuit

Thermostats start to open at around 80°C and give around 90% bypass ,when the bypass is closed it gives around 10% bypass to maintain prime and to not allow a cold slug of oil entering the system when it operates. Oil cooling inside the engine is more efficient at removing heat from internal moving parts than air cooling on the outside of the engine.

That said the 'cool jugs' product or anything that helps the dead air on a full lard FLTCU definitely helps get rid of a lot of unwanted radiant heat which the guys that ride these bikes and their passengers legs can attest to. As for idling in traffic on a hot day ,it is an unfortunate byproduct of our activities but i would be reluctant to arrange my bikes cooling features around this one circumstance.
A while back on a ride between Swan Reach to Loxton my engine temp was slowly creeping up towards 145°C .{normal is around 100/110°},i varied what was already a fair rate of speed and actually found that going a bit quicker stabilized the temp ,,, when i got to Loxton the servo lady informed me it was 44° outside! and the bike did not miss a beat . {and no cooler} i use Rock Oil guardian 5-50 semi synthetic.

15-50

^
are these figures, or some that are slightly more 'alarming' ... cause for on concern ?

Yep ....

Uncomfortableness is one thing.

Failure is something completely different.

I can cope with both !

I bought a HD oil filter for my 88,the thermostat cuts in at 185 degree...
It works well

http://www.harley-davidson.com/store/premium-oil-cooler-kit-pa-04-2615707--1