6NT turned out to be the best contract on these hands but my partner and I didn't bid it. Please can you explain how these 2 hands should be bid. I held SAKQ87; HK54; DA; CQJT3 and my partner held S4; HAQJ8S; DKQJT; K84. My partner opened with 1H and although I had 19 points opposite my partners opening bid, I thought it was best to just change suit to start with (as this is forcing) so I bid 1 spade. My partner then bid 2 diamonds and I jumped to 4C to force him to bid again. An opponent asked what this meant and he said he thought it was a splinter agreeing his diamonds, and then bid 5D which I took to mean (as I knew he thought it was a splinter) he didn't think slam was there. Not knowing if there were 33 points between us for 6NT, I bid 5NT and made 12 tricks. Our opponents were vulnerable and we were not.