I build one from 1.5mm airplane plywood. It weights ca. 12kg/27 lbs. I test it on hiking trip in Lapland and it was great fun.
Backsplash  –  a backpack kayak  (3130 x 670mm   10` 3 ¼” x 26 3/8” )
With backsplash it is possible to combine hiking and paddling during same trips. It has separate carrying system which is comfortable and strong.  Backpack frame can be stored over back deck while paddling and hiking gears can be stored inside hull while hiking. 
Below is links for rotatable 3d models. They work best on computer, but can also be viewed by phone. It takes a while to load model. Exit model by clicking back on browser. 
It can carry ca. 100-110kg/ 220-243lbs load (including boats own weight). I do not recommend packing any more load for that small boat. I also have drawings for version which can handle ca.10kg/22lbs more weight. It works as supplement to original plans. If you are interested of that you need to buy original plans and email me so I will send them via email. ( note new update at the end of page - new version will give possibility to build both versions to same middle part ) It would also be handy on fishing trips to remote lakes or as project when building or storage space is limited.  Living on city? – take a boat on your back and walk to shore to for paddling?
Note new update - see bottom of the page
Update!  I am building longer bow and stern parts to my Backsplash. Middle part is same as in original design and I can change stern and bow parts when needed. If you have already build original Backsplash, these longer parts will fit to yours boat as well. It may not look big difference, but these parts will let you pack more gear to boat ( mainly  over back deck ) without letting stern go too deep. I will update plans after I test new longer version. If you like to test longer version, please contact me.
I build one from 1.5mm airplane plywood. It weights ca. 12kg/27 lbs. I test it on hiking trip in Lapland and it was great fun.
Backsplash  –  a backpack kayak  (3130 x 670mm   10` 3 ¼” x 26 3/8” )
With backsplash it is possible to combine hiking and paddling during same trips. It has separate carrying system which is comfortable and strong.  Backpack frame can be stored over back deck while paddling and hiking gears can be stored inside hull while hiking. 
Below is links for rotatable 3d models. They work best on computer, but can also be viewed by phone. It takes a while to load model. Exit model by clicking back on browser. 
It can carry ca. 100-110kg/ 220-243lbs load (including boats own weight). I do not recommend packing any more load for that small boat. I also have drawings for version which can handle ca.10kg/22lbs more weight. It works as supplement to original plans. If you are interested of that you need to buy original plans and email me so I will send them via email. ( note new update at the end of page - new version will give possibility to build both versions to same middle part ) It would also be handy on fishing trips to remote lakes or as project when building or storage space is limited.  Living on city? – take a boat on your back and walk to shore to for paddling?
Note new update - see bottom of the page
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Update!  I am building longer bow and stern parts to my Backsplash. Middle part is same as in original design and I can change stern and bow parts when needed. If you have already build original Backsplash, these longer parts will fit to yours boat as well. It may not look big difference, but these parts will let you pack more gear to boat ( mainly  over back deck ) without letting stern go too deep. I will update plans after      I test new longer version. If you like to test longer version, please contact me.