My friends took plastic (Paris brand, like for Denali) sleds, but I think one of the outfitters in Chalten had one fiberglass one that they borrowed too, not sure. Best to take one I'm pretty sure.
I think I remember them saying that they only used horses to save time, but that it would not have been too hard to just do a couple of load carries. Also the horses cannot carry right up to Paso Marconi, they stop short, so you have a short double-carry anyway, I think.
My friends did Mariano Moreno, mostly on skis, in a very long push over a day or two. They never got near Lautoro on the second trip. I don't have any beta on Gorra Blanca or Solo, though you could check on GoogleEarth, if you haven't already.
There's some topos here: http://www.expe.com/montagne/ams/patagonie/gpchal.htm
but nothing for Gorra Blanca and not much on Solo.
Also, another friend made the first north-to-south traverse and wrote a book about it:
This book has maps and photos and a history of traverses, but nothing on those specific peaks.
I've PMd you a couple of contacts.