I have 2 Honda 2000i gennys and have tried storing them in the front pass-thru storage on my 22FB. No matter what anyone says - you can really smell the gas and exhaust form them - when the trailer has set still for a couiple of hours.
First thought was to put a box on the back bumper - but was soon talked out of that on this forum - without a lot of extra work to strenghen the back bumper - which kills the warranty.
I got exicted when I saw the diamond plate tool boxs many have added to the front of the trailer. But none were the right size to hold the Hondas - and fit in the space between the front of the trailer and the propane tanks.
So I built my own boxes - they mount of the front tongue of the trailer - they are held up by two 2x2 metal shafts bolted to the tongue.
Also can now carry 2 batteries.
Not worried about tongue weight since the gennys used to ride up front anyway - plus I tow with a 3/4 ton that has 1 ton springs (used to carry a 4000 lb + truck camper).
I don't carry them in the back of the pickup because my two motorcycles take up all the room.