Home built roofing shingle lift

Designed and built this shingle/material/tool lift to use when helping my Dad roof his house to get around the worst part of roofing -- carrying shingles up the ladder. Designed in Autodesk Inventor using some old elevator roller guides and hatch door rollers as pulleys (both ball bearings). It is roped 2:1 so the person pulling has to walk double the lifting height, but at half the effort. The rope was 3/8“ poly rope rated at around 250 lbs so 2:1 the rope would suggest 500 lb capacity. As an engineer, I w