it all depends...
if you've raised the large capital base through your trading, then ..NO =if it ain't broke , why try and fix it?
if you haven't and have otherwise managed to accrue that big pile through other work..then that's another matter..
still further, what might be sizeable trades to you is chicken feed to one and impossibly large to another.
sounds like you know compared to your peers you're donig well, yet you yearn for fullfillment, which at this juncture, you are choosing to define through your work as larger trades on the same instruments..is that where you're at, i wonder.
jesse livermore was an advocate of not using more than 10% of your capital base..
tere is a view that too small a % can introduce sloppy trading as there is no risk, as such to your pile. too big and a big hit on a bad day etc...
for me it's more a case of determining your trading style through experience. let's say your a day trader using the 1/5 min charts on the dow [me!] to get your fill easily in an instant, assuming you're using a spread betting firm, may limit you to £20 a point.
this , then , is your bench mark by which you can trade effortlessly. anymore and you introduce hiden stresses as you may not get filled=unconfortable feelings take over etcetc
so, you either accept £20 is a max and enjoy it or try position trading [say the 10 min chart] use the phone and place £100 positions..now how would you feel? or even a £1000 as with IGindex or 50 lots on their CFD's [500$ point]!
% of capital can be uselessif your trading style/natural rythym works best at say trading the 1 min dow..etc
if your a position trader[dailys] then 10% makes sense on margin
as you can buy 10 times the amonut of stock..but your stop loss MUST be 10% or less to protact your remaining capital, risking only your deposit..as wel you know, i dare say...
it's down to your trading style really..have you outgrown your £££?
or did you have a pile to begin with? whats your sizable bet?? and on what??