Jack, this model is designed around their (Hangar 9) Evolution engines. Their carburetors are at the front of their gas engines just like the glow fuel engines.
With the DL as you obviously know the back mounting makes them too long for the design of the mounting system.

You haven't mentioned by how much the engine is too long.....

From what I can see, there is no way to mount the DL unless you consider Sandy's suggestion or a variation of that.

Can you post a pic of the inside of the firewall area so we can see what is behind it?

Sorry I'm so slow responding Jack, I was out at the camp all weekend.
It doesn't matter which mount you use Jack, but don't forget you want to have the prop hub set to whatever distance from the firewall the instructions call for so the cowl will fit properly.

I've cut mounts a little to make them shorter or put plywood "shims" behind them to lengthen them to get the desired distance.

This is not an option for a 10lb model, what are they thinking

Looking real nice Jack!

Come on Mike, come to the Dark side....

Jack, remember do not remove the spring just trip the small wire tip off the cam arm. Leave the spring intact and on the shaft it keeps tension on the throttle shaft and not on the open close movement.

You won't be able to see the throttle movement very well as the carb is mounted close to the firewall so, ensure your throttle servo is moving correctly. Open is open and close is closed.
Some radios often need the throttle servo channel reversed  to match the correct carburetor movement. 

hope this is helpful.

Looking good Jack, even with Dan's help