construction ideas

i have been looking up ideas on how to build a trebuchet and i found these 2 photos on google on someones trebuchet and it looks like it would really work and it one of the ideas i would like to use. i will have to research  ore on the sling as mr ward tried to do it but it didn't work for him but i would really like to give the sling a go as it would make the golf ball go further when we test it on the oval.