Pack your sea bag like an old salt. Here's how:
We've all seen them, the sea bags that come from a crew member's previous military service or a sweet deal at the surplus store. They're durable and easy to stow but sometimes it's hard to fit all of your gear into one without some wasted space. It's also handy to know how to pack one if you're shipping a departed buddy's gear back to his house for him. It never fails. You can show up to the boat with one bag and when they send it back to you, it turns out to be one bag and three boxes. Try this out and use every bit of space available in a sea bag.
First, you roll the sea bag down like a big condom. That's right. That sounds a little coarse, but it's the best example of how to do it without going into a lengthy discussion. The picture below is a good idea of how the bag should look before you start.
Then you begin placing your clothing into the bag. This one has a few items in it. As you can see, you should work in a shallow area packing the clothes into the small space with no empty places. The shallow bag is easier to work in since you don't have to reach in all the way up to your arm pit.
As you fill in the space, roll the bag up a little at a time to make more room, packing tightly as you go. Soon you'll have a bag that looks like this.
If you get all of the soft clothing packed in tight, you'll have room at the top of the bag for your shaving kit, boots, and other odd sized items. Give this a try and see if it doesn't help you fit more of what you need for your hitch into one small space.