Watch Nadal and Federer...
The reason they hit with a straight arm is that they perform an arm extension in their take back while they pronate their forearm a bit. I've posted pictures of Federer's forehand in a few threads. I'll try to get them as they are commented with the actual anatomical terms which tells you exactly what movements he performs in each pictures.
I used to hit with a straight arm forehand. I spent the whole summer last year figuring out how I would get to hit it a la Federer. Of course, it worked fine. I was blasting the ball really hard and I had tons of spin... I spent so much time working on my footwork and shot placement that I was able to slam almost any ball I could get to. However, the timing and contact were really hard to get right and every other day I would be hitting very averagely. Kudos to my hitting partner who started hitting big himself and getting me into trouble, but it wasn't only about him playing well. It wasn't rare to play two or three great days and then have a poor day... and I had a one handed backhand, not to help! So both of my strokes used to be high maintenance.
But if you say that you have a good forehand right now, why not work on improving what you have instead of trying to change it all over? I recently got enough of trying to maintain a super high level of play to be aggressive all the time. Instead, I work on movements which are easier to duplicate. I have a two handed backhand since three weeks and I must have played a few thousands of them by now -- it's not yet a second forehand, but it evolves greatly. I started using the double bend and a genuine western grip and I'd say I'm hitting about as big as I used to, except with more spin.
And, tactically, instead of trying to end the point early, I think I'll get to build them one shot at a time, knowing I risk not to miss too many of them. If you really want an advice, getting grooved in a simpler movement will pay off in the long term; if you get to stop and play again after a while, your movement risks to be closer to its previous level if it's simpler and, throughout matches, you risk a lot less to ride roller coasters where you will hit either big or fail.
"A nation that asks nothing of government but the maintenance of order is already a slave in the depths of its heart [...]." -Alexis de Tocqueville