It is my understanding that you can no longer have separate accts. I asked to go back to my commodity only acct. because of IB's , to put it mildly, rather different bookkeeping methods. Was told no dice. Can you imagine trading ten-years in 64's and then seeing them marked to the market close that happen before you made the trade, and in decimals? Try and remember where you traded something 2 or 3 days before, and have to look through your emails to find the execution price , then convert from decimals to 64's. I might have done that in my head 25 years ago but no more. And your monthly statement? As Tony S. would say, "Forget about it!".
You can open as many accounts as you like, it's just that they have to be Universal now apparently. That doesn't stop you from trading just commodities in one, and just stocks in the other. Can you describe more clearly your problem with fractions and decimals? It seems to be aimed at people who already know about it (which I don't).
Yes you can trade just commodities in a universal account. But funds are transferred back and forth from the stock portion of the acct. every time you go in or come out of a commodity trade. If you had traded the 10 year at the last price traded the execution would have been at 112'265 . That is the format in which you trade the price on the IB screen and the manner in which it is reported in Trade Station. This is 112 plus 26/32 plus 1/64 or 112 53/64. When you get you statement from IB the next day the price is reported as 112.8125. This is 53 x .015625(1/64) = 0.8125. Now make a number of trades in and out thinking in the first format all day and then look the next day at your statement the next morning in the decimal format and see how easy it is for you to reconcile the trades. (We all do check our statements to see that the trades hit correctly don't we?)
Why is that a problem, though? It doesn't really affect anything, in my experience. I have a U account that used to be a futures account, in which I only trade futures. I assume you meant 112.828125. We equity traders went through this pain some time ago. Such is life, I guess. I can't really fault the back-office developers for wanting to unify everything in decimals now that there are so few remaining non-decimal markets. FWIW, I've never had an issue where I executed in TWS and the price came out different in the execution report than I expected it to - certainly not against me. I auto-import and cross-check my execution reports against my statements nightly (well, the next morning lately with IB's statement delivery being so slow lately ).