I am attempting to construct a small glider that will stay in the air for the longest possible time. Can a biplane style work for this? The information I'm getting doesn't say anything negative about a biplane.

The max wing span on it is 40 cm with a max wing chord of 10, so I thought having an extra wing beneath the first would have an advantage.
Also, there is a weight restriction, will the benefits of a biplane counter the negatives of the extra amount of weight?
Would the rear horizontal stabilizer also need an adaptation for this?

Any help would be wonderful, just keep in mind that this isn't my main hobby so I may get a bit confused.