Property co-ownership in itr2

Me & my wife purchased an apartment in 2008 and both our names are mentioned in the sale deed. The %age of co-ownership is however not mentioned. We also took a joint loan. The loan is a 'homesaver' type where a linked joint current a/c allows us to keep our surplus funds and reduce our loan interest payment. We just put all surplus here and do not really pay attention to the %age of money put. The EMIs are picked from this joint a/c by the bank.

I'm in the 30% tax bracket and my wife in the 20% tax bracket for the past few years. Also the total interest paid has been between 2.5lakhs to 3lakhs for FY2010-11 as well as FY2011-12. For FY2010-11, I claimed 1.5lakhs and my wife the remaining amount. This year (FY2011-12), the ITR2 form is asking for %age of co-ownership? Can I claim full 1.5lakhs and my wife the remaining amount? Or is it safer if we claim only 50% each?

Kindly advise.