I've seen videos on grass so I know it can be done. What fan are you using?
I've got a Stumax ready and waiting for me to get time to install and also plan to have a go at grass. I'm shooting for ~10-11 lbs on 11S 5000 XPS cells.
Our field gets very soft in Spring and Fall, so I plan to maiden in summer when the runway is harder. Tamjets has some nice shock absorbing landing gear struts you might consider:
http://www.tamjets.com/gear.php
I think big wheels are key. I bought 2.5" Maxx products aluminum hub main wheels and a 2.25" dubro nosewheel with shock absorbing strut from Tam. Brakes too but probably wont' use them at first (no need on grass).
I may also try to work in some carbon "flex plates" on the main gear mounts if I can find room like BVM have for their jets.
Do some searches in the Spark thread on RCG and you should see at least 1 video of grass takeoffs. Maybe also search for "grass" within the thread.
Joe