You think bonds and stocks are both risky, yet you propose shifting your allocation more to stocks and less to bonds. If you really think both are over-valued you should purchase something more secure like GICs, but that would be market timing which very few here will advocate. As Retire-Canada said, stick to your investment plan or investment policy statement. If you don't have those, give it some thought.
CBO has mostly AA and A rated bonds with a duration of 2.99 so it should not be too volatile or risky. Go to iShares.ca and compare the performance chart of CBO to XBB, and you will see how much less volatile CBO is. Remember that as rates go up, bond prices fall, and the longer the duration the more they will fall. CBO's duration is relatively short. But then as bonds mature or are sold off and replaced with new issues, the yield will rise, driving the return back up. See this CCP blog post that explains as long as you hold a bond fund for at least its duration you should not lose money because the yield will offset capital losses.
http://canadiancouchpotato.com/2011/07/07/holding-your-bond-fund-for-the-duration/This blog post discusses both VXC and XAW and taxes
http://www.canadianportfoliomanagerblog.com/war-of-the-worlds-ex-canada/This has more info on taxes
http://canadiancouchpotato.com/2016/07/11/foreign-withholding-taxes-revisited/You can avoid some withholding taxes by holding US domiciled ETFs like VTI, but that brings other challenges like currency conversion headaches.