If you are consistently putting it in the net, the issue may be you don't have the power to make this a good shot in a match. If you are running hard out wide to your forehand side where you are pulled off the court, you can do a lot more damage potentially by going DTL. Pace and penetration is a lot more important to winning that point as opposed to a cross court weak shot.
Another thing is you'd want to flatten that shot out because you will probably get a loopy, great angle, but also a lower powered shot that is potentially easily covered/anticipated shot by your opponent. I am envisioning when you are in a position to hit a crosscourt on the run FH, it's very likely a good player is going to already position him/herself to be neutral on the court or be coming to the net. If you hit a weaker cross court FH the opponent will close out the shot with a drop shot or just put it away. My 2cents says I'd rather take a shot going DTL with the best pace/heat on the ball that is more of a challenge for your opponent to hit.
But to still develop that shot, I think you need to flatten the FH out when you are going for the cross court shot. I have a heavy TS forehand like you as well and I use an open stance, as I suspect you do for your normal, solid fh shots. The problem with type of stroke setup is our power is generated by waist and shoulder torque. When you are on the run, you just need a ton of "replacement" power for not being in that stance so I'd look to get some extra oomph from a flatter shot/wrist position. Remember your bodys momentum is pulling you away from the court and also diminishing the power you have.
Another thing is timing, hard to do but you need to strike the ball as early as possible meaning you need to get that racquet accelerating earlier than you think.
This is one of the last shots I need to clean up. Running out wide to the forehand, and because of the great angle, I often want to put it CC to the serviceline - sideline area. I can usually pull it off more or less, but when I miss it is ALWAYS low into the net. I don't have the same problem putting it back in the middle or DTL, or if I'm not running to the ball. Oh, and I am always trying to hit my normal SW TS forehand.
What are the special considerations for this shot, and how can I adjust to get the ball up more?