Hi,
um.... is the question whether 26% is too much serious?!? Please try to find a street with about 15% slope, you’ll hardly find one and for good reason! At 26% you will already have real problems with an empty wheelbarrow, better not even talk about a full one! Just off the top of my head, I’d say that more than 10% slope with a full wheelbarrow will really be difficult.
Best regards,
Andreas