I also tried the same. But i faced some problem..After that i migrated my application from forms6i to forms10g with help of Code One Solutions [p] Ltd.
They are specialized in
Oracle Forms Version 2.3 / 3.0 / 4.5 / 5.0 / 6.0 / 6i to Oracle Forms Version 6i / 9i / 10g. Oracle Reports version 2.0 / 2.5 / 3.0 to Oracle Reports Version 9i / 10g. We also do migration of other objects such as Menu / PLL / Pro*C to the latest version. We also do multi language migration which includes Japanese, Arabic, Korean, Chinease among others.