FYI - Support for backfill for IDEALPRO (Forex) via Interactive Brokers will be available in the next beta version (3.6.1F)
10 days of data through QT on all IQFeed symbols. They don't support all IB symbols. All US stocks and futures. some Asian markets, some others. would have to check on IQFeed web site.
FYI - QuoteTracker version 3.6.3H (released today) has support for 5 day backfill using Interactive Brokers as the datafeed. NOTE: Best results with TWS version 849 or higher. http://www.quotetracker.com/beta