The 1:7 system do indeed pull harder on the leech then the 1:5 systems of the past but the modern mainsails do require alot more leech tension then the mainsail of say Hobie 16's etc.

Personally I think it is more effecient to find your self a really flexible sheet line of a modest diameter. This will have significantly less friction in the system and allow you to pull harder on the leech. Best is to also have a second ratchet on the mainsheet just like on the spi sheet.

Wouter