Can you define heavy duty? This is a loose erm. My hi-start is based on 1/2" tubing with 3/32 wall and was not called heavy duty.

The Dynaflite Heavy duty hi-start uses 3/16 id and 5/16 od tubing with 350 feet of line. They claim this will handle planes of up to 120".

What are the specs on your HD hi-start.