One headache mobile developers have to grapple with when they want to test new ad units or user flows is having to retool then resubmit their app to the store.

San Francisco-backed company PlayHaven says it can fix that problem through a new service that places an HTML5 overlay on top of a developer’s app, allowing them to quickly swap in and out different types of units.

Many of the bigger developers like Storm8 already handle most of their content on the server-side, so they can quickly put new items in their store or test new cross-promotion campaigns. But smaller developers lack this advantage so PlayHaven’s product could even the playing field for them. PlayHaven is comparing it to a content management system or CMS, which made it easy for people without technical backgrounds to handle updating their sites quickly.

“Developers complained to us that there were too many SDKs (software development kits). Any time you want to try some other way to monetize or a new feature that you didn’t want to build yourself, you require another SDK,” said Andy Yang, the company’s chief executive.

Each SDK can also add to the size of each app, bringing it closer to the critical 20-megabyte limit at which Apple forces users to download the app over wi-fi instead of over the 3G network. Passing this limit can drastically drop the number of users who choose to download an app.

Adding PlayHaven’s so-called “dynamic overlays” allows developers to test different interstitials and promotions without having the re-work the app itself or resubmit it.  (That said, if you test a mobile banner unit that will cover up a critical part of your game’s user interface, you might have to reformat it to fit.)

Accompanying the overlays is an analytics dashboard that shows the clickthrough and conversion rates on these units. If it’s a cross-promotion ad, then it can also show actual installs facilitated by the unit. Developers can also control the frequency with which promotions are shown, or put time restrictions on them, just like with many advertising products.

The service is free for the first 1 million messages a month and then 10 cents for every 1,000 messages after that. A “message” is like an interstitial or unit that’s exposed to a player in the dynamic overlay. PlayHaven just signed a big contract with Glu Mobile to test its dynamic overlays in the company’s games. Before that, it said it had 36 million unique users and was doing 150 million game sessions a month.

The company has raised $3 million last year and been through a number of changes over the past two years. Yang stepped up as chief executive at the beginning of the year and the company shifted away from being a social network for gamers.