I made a raspberry mead (melomel) once. I lost the recipe due to a hard drive crash and several moves since I made it but off the top of my head I think it was 12lbs of local honey and about 4lb of raspberries added in the secondary. It took an extremely long time (1 year+) to clear and should have gone another 6+ months to be honest. It also tasted like a shot of vodka and then some sweetness for the first year after bottling. The raspberries added a ton more sugar so the ABV shot up and I didn't adjust my initial honey addition accordingly. After about 3 years from originally being made it did come together and was something along the lines of a raspberry like wine...sorta.
If I was to do it again I would:
- Try several small batches before a 5 gallon batch
- Adjust the initial honey addition to compensate for the raspberry addition
- Learn to back sweeten mead (same as wine I think) since I like a sweeter mead
- Let the mead go until it's ready to bottle...not when I feel the need to bottle it
Maybe not the greatest of help but hopefully it helps some.