Shotgun primer nipples for Ruger Old Army

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Hope I'm not being an annoying newbie and asking a previously answered query but the search function seemed to not let me search in the muzzle loading forum only.
I've seen members mention that they use them but not discussion around the difference between these and usual primers pressure-wise.
Please note I'm not suggesting using Nitro for all the obvious reasons but I do use 777 rather than black which has a pretty high recommended load of 30-35 grains.

So, I've seen the drop-in replacement nipples for the Old Army allowing use of shotgun primers which sound great (though the line 'They do require a degree of experimentation to obtain the optimum performance.' Is a bit of a concern...)
It's a temping idea as 209 primers should give more consistent ignition and be a lot less fiddly and be less likely to chain fire which all sounds like a step in the right direction.

I'm guessing they give a lot more oomph than standard primers so do I need to consider this in terms of charge, taking into account that to keep within the fairly tight recommended load of 777 I don't have much leeway? Or because of this are they simply inadvisable?
http://www.anvilconversions.co.uk/in.../Page13768.htm

Any thoughts very welcome. I'm very cautious to stick to 777's loads, as you probably know the 777 website now states that you should only use one specific charge for any firearm (it lists BP pistols and rifles and their recommend 'dose') as well as saying that you must not use filler and only one wad.
This has changed in recent years and is due to the fact that 777 unlike other propellants in very sensitive to how compacted or loose it is and different loads can lead to spikes of pressure.
See here for info
http://www.hodgdon.com/loading.html#
And here for load data (see cap and ball revolvers at the bottom) http://www.hodgdon.com/PDF/muzzleloa...?CHECKBOX_1=on

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Friday night bump in case anyone is about who has any thoughts