They are already playing divisi; two parts per stave - having four parts on the one stave would get really confusing.
I tried doing it double stopped, and the same thing happened - the score got cluttered and it was difficult to read.
I'm not asking anyone to write it for me - I just don't want to get tangled in the logistics or find I've written parts that aren't well suited to the instruments
[edit] I think I've got round this by arranging the score so there are 2 staves for violin 1, and two staves for violin 2, each divisi, allowing me to get the full chord - which will hopefully mean not having to add extra violin sections