Hi there - saw this one and thought I'd let you know I sold my entire record collection and what was left of my father's collection and made some very good money doing so.  I purchased the record mailers which you can buy on Ebay and put that cost of I think it was $1.80 a mailer on to the purchaser.  I also put it in the ads for the LPs so it was transparent to the purchasers that I was charging that on top of postage.  You can fit 4 vinyl LPs into one cardboard record mailer. 

The rarer the LPs the better - for example, fringe or independent music LPs did very well for me price-wise.  I did have to also box up a large amount of LPs I sold to one purchaser and I found a size appropriate box for alot of LPs at Officeworks.

Good luck with the selling!