I'm getting ready to update the lite version of my game OmniBlaster (http://bit.ly/omniblaster and http://bit.ly/oblasterlite) to get it up to version 1.2 like the full version.

The lite version, while being out a month less than the pay version has roughly 10x the downloads, which I would have hoped would have been a lot more. Any way I've not see anything that looks like "Lite conversions". In the game, I have an "Upgrade" button, though the button isn't in the same style as the rest of the menu. There really isn't a "Call to Action", so I'm considering changing the upgrade prompt to be a little prompting with a call to action.

But how do I do that.

The easiest route will be an alert box with a "Yes", "No", "Not Now" option and direct them to the iTunes store to spend their hard earned 99 cents.

I could do a stylized screen, with some marketing about why they should upgrade and do graphic buttons, which is of course more work.

Which would be better? When should I prompt for an upgrade? When they get a game over? After they loose a couple of lives? After X number of levels?

Or should I go in-app purchase, and give them the opportunity to visit the "Ships Hanger" to buy upgrades to the two larger ships, which they earn in the full game?

If I go that route I would need a stylized screen to let them select the level of upgrade. The nice thing about this is it can be more revenue because I can get two purchases for each of the ship upgrades. But if I do that, when do I give them access to OpenFeint and the other features the freebie doesn't get?

And do I add Ads in now that we have the AdMobi code to work with?

I know its a lot of questions but I could use some advice and suggestions.

Thanks
Rob