Since you mentioned trying a heavier gas engine I suggested the Giles because it has more wing and stab area than the Katana.
Take a look at my RCU post at Post # 191 on page 8 in the "ULTRA RC KATANA XTREME - new release" thread, http://www.rcuniverse.com/forum/m_48..._8/key_/tm.htm . There you will find a little comparison. If you have any other questions I will try to answer them.

Keep in mind that the opinions of others may differ from mine if their setup is different. However, you might have noticed that the Ultra R/C Giles 202 UL 29% thread is one the biggest with 106 pages, 2643 replies and 130,378 hits and you'd be hard pressed to find a negative post about the way it flies.