Just for consideration I pull a 3pt 20 pan 18" disc (7.5" spacing) weighing approximately 1000lbs behind my L3560 (has rear wheel weights & loader) over a relatively flat (<4% grade) garden. The tractor is definitely working under load, but it will get the disc to suitable working speeds even with the disc dropped all the way ... assuming soil conditions are appropriate for working (i.e. friable not muddy or rock hard).
With the 50lbs per pan weight it does better as secondary tillage than primary, but it can still chop some virgin (and unplowed garden) ground if pitched correctly (have a clay/loam soil). I leave the garden "headlands" unworked so end up tearing up some turf on each pass through the garden, and don't plow winter cover crops in ...just disc and spike harrow them. The heavier per pan weight of a pull-type should help with that even though it's not the ideal set up for breaking new ground.
If working large areas at a time you may want to keep an eye on the hydraulic fluid & transmission temps and take a break to let things cool a bit when/if needed as I've noticed when doing other heavy work that performance can drop off when the rear housing has started to feel warm/hot....may not be an issue with the larger Grand L's, but something to consider.
Also, if you find a problem area the draft load can always be reduced by lifting the disc to reduce tillage depth, or changing the gang angle. So even if it's not ideal I'd suspect it'll work and perhaps leave a better mix of soil clumps/fines than a tiller would....and depending what you're planting it may also useful to work in broadcasted seed by using shallow tillage depths.
Just my :2cents: though..... (which may or may not be worth that much :confused3: )