Thanks Ian. The carbine is actually a very attractive piece -- if you can get out of your mind what it looked like before being converted (something that is hard to do, especially for all of us who love Enfields).
Your idea of putting on a rear handguard, especially a grooved one, might be a very interesting modification of an sporterized model that has the barrel snipped and the foresight reconfigured. I wouldn't do it to mine because it would mean replacing the fore-end, which has been shaved down to make it more delicate. But it is certainly an option for those who just don't want the sporterized look and cannot justify the economics of a replacement barrel or a reconfiguration of the muzzle to original specs.
The fore-end is birch (Savage) and the nose cap is a stock Savage sheet-metal nose cap that has been reduced in length and one new hole repositioned for standard retaining pins.
If you check
Long Branch - Linking Serial Numbers to Month of Production, you will see that LB didn't get a directive to start engineering on the No.5 until April 1945. LB could have used a 1944 barrel and receiver for their prototype, but logic would say that after making lightening cuts in the barrel and receiver, any prototypes would then be stamped "1945." It could be if you saw a '44 LB No.5 it was a retro-fake. However, I am not an expert at this micro-niche in LB's history, so I will defer to several others who are better informed.
Glad you got a rare LB 800 yd sight -- those can't be very common.