I'm with IC on making a puree first; you could even roast the raspberries first, to really concentrate the flavor. I've made it using apple cider vinegar, or Japanese rice vinegar, and it's fine; I find the white vinegar too overpowering. And yes to the safflower oil, too.
I'm trying to remember - I did a vanilla/pear dressing for a catering gig once - I think I used a half cup of puree, 1/3 cup of vinegar, (I used a pear vinegar I found at the store, but either of the above would do fine, I think), 2/3 cup oil, salt, pepper, and some minced shallot. I did add a shot of pear brandy, too - if you have some Chambord just lying around
a shot of that would be great!