As mentioned by eighty8fierogt, in response to your thread, most people, from what I have read, stay away from the Heavy pellets, for fear of additional wear and tear (stress) on their spring guns.
I'm not sure about Kodiaks, but, with Crosman Premier Lights, 7.9 gr, I get around 950 FPS out of my Alpha Chrony. This is at about 1000 feet above sea level, a few miles off the Puget Sound, in Washington state, where it tends to be mildly to moderately humid, on days between 50 to 70 degrees.
If there are any Kodiaks in .177 at my friends house, I'll try to remember to Chrony some shots with my Viper and get some numbers for you. If I recall, shooting Crosman Premier Heavy, 10.4 gr. pellets, I was getting around 850 FPS. I'm not 100% sure, since I Chronied a lot of different ammo and stuck with the Premier Lights.
For more information on the Viper, you can check out my review:
http://www.reviewcentre.com/review247473.htmlAs well as all the other reviews and opinions:
http://www.reviewcentre.com/reviews108126.htmlAs well as some reviews here, in the Product Reviews section:
http://www.gatewaytoairguns.com/airguns/forums/forum-view.asp?fid=15Personally, I really enjoy mine and I don't regret purchasing it. I would do it again, since I prefer composite stocks, over wood, for practical purposes of durability, ease of maintenance, reduced weight, comfort, feel, etc.. The only change I would make would be the previously mentioned be adding/changing the trigger with at GTR-III trigger, maybe a Turbo Tune and it would have been nice it it came in a Nickel Plated or Stainless Steel version. I may even consider buying a second one and have it Nickel Plated, if they can do it without plating it effecting the chamber and such. I have to research that a bit.
Good luck.
Tim