So I found out how to place an env_sprite or cycler_sprite in hammer and set its "sprite" field to a "model" without crashing hammer. Just take the model out of its folder and than in hammer create your env_sprite or cycler_sprite and set its sprite field to the model with its original location and everything. Than compile the map. It will not run saying the model cant be found. Than just place the model back in the folder and run the map and it will work! This is great for things such as grass models being walk throughable.
Also I converted de_plaka to a map file to see how they made their seagull fly and they used a cycler_sprite so it is a must to get the flying seagull model to work in your half life maps!