swoop223,
1. no mentionion of a minimum deflection requirement - it is a maximum amount - meaning it shall not deflect more than X, Y or Y values plus no welds shall break, or if they do add a gussett & retest. I am well aware of these standards - I was working in the lift truck industry in 1969 or 70 for two or three years when the first OSHA standards were published primarily for employer compliance - most lift truck companies that built trucks in the US had been building & testing trucks to comply w/ANSI B56.1 many years and using SAE testing methods as a standard prior to OSHA regulations be coming a Federal Law. Today's OSHA laws have evolved over the years into today's standards & some names have changed and various standards combined to simplify life (sort of) for all.
2. the standards are set by SAE (formally ANSI, ANSI/ASME) by a capacity range - the manufactuers have in put into these standards but a ALL manufactuers in teh USA must comply to these standards. OSHA does not write too many standards the adopt know & well recognized standards - like SAE, ASME, ANSI, etc. etc. Lift truck manufacturer build a family of trucks on a given wheel base to which an OHG of a specific length, width & height will fit - e.g. a 3K,3.5K, 4K lb. capacity units. The manufacturer will test the OHG integrity according to the standards set forth in the SAE standards for teh manufactuerer. Often, manufacturerer call a family of truck, 4K, 5K,6K & 6.5K units but thewheelbase will change and "generally" but not alwayss, the OHG length will change so the 5k unit w OHG will be tested & the 6.5K will be tested against the guidlelines. & so on.