Matt or someone else would be able to answer the above question better than me..
Okay I'll bite !
The Viper has a 4:1 purchase system betweent the sail and the bottom of the mast; you can see it in the 4th picture.
The total system is a 16:1 and that means that the (single) blue line that goes up from the beam to the sail will only see 4 times the load that you pull on your downhaul line. Typically a human being does pull more then 50 kg; Therefor the force in the blue line is typically 200 kg or less while the total downhaul force on the sail may be around 800 kg's.
A normal boat of F16 dimensions will quite easily see up to 1500 kg in mast step loads. Afterall the mainsheet tackle alone will already induce close to 400 kg of compression on the mast foot. The forestay and sidestay add similar amounts to the total.
Going up from say 1500 kg to 1700 kg (13%) is not a big deal at all.
Wouter
