Hi, I'm installing a 110 ft, 6 degree, Allen Block retaining wall into a bank that starts and ends at 0 feet and will be about 7 ft in the center. I'll be using geo grid every 2 courses, 3/4" crushed ledge backfill, drain tile, and I'll be compacting every course. The base will be 2' x 2' - 3/4" minus screened, crushed, washed stone. I've yet to check the product guarantee, but, I'm curious how many year guarantee I should offer the owner. I welcome any constructive input? Thanks.