https://www.kifaru.net/paratarp2009.html
depending on your touring, weather, etc...
i have this to say about shelter...
generally, the bigger it is, the more time you're going to spend in it.
if you're trying to spend time on the bike = mileage
the more complex your campsite, the more time you spend setting up/tearing down/packing, etc...
you can try to use sticks,
you can mark alongside the tarp, a pre-measured length.
in that you may use that measure to break/cut a piece of deadfall to suite the need.
a cable saw is light, and works well for these types of light duty
http://www.survival-gear.com/wire-camping-saw.htm
or if the tarp has eyelets atop the pole inserts, you could string it from a limb up above, tie a rock to the end of some nylon cord and toss it over something.
as in the way i have this tarp pitched. no poles.