How about some pics of yours!
If you look at the first post here there is a link to my build thread. If you go to the last 2 pages, there is very detailed info [with graphs]on the weight and flights. I chopped it and downsized the hardware to 3/16.
But to summarize . I cut off the unneeded tubing [18in tot.]and eliminated the 4in altimeter bay body tube. [cut it down to 1/2in]. Also trimmed down the fins by about 18%.
Done , painted and ready with 2 alts and batteries, sans motor....7lbs 4oz.
I saved about 1 and 1/2 pounds by what I did.
My old one was only 5.5 lbs. RTF, but that was with thin wall tubing, and lighter NC., which is no longer available. I built the new one to the same length and specs. as the original. but the parts are now much heavier. Mine is 60in long.instead of 78in. Don't need it, didn't use it. Also by being shorter, less drag.
That one went 15,300 on a K-250 and 13,400 on a AMW K-750
With a AMW 1050 and J 357 GG [?] 10.2lbs and 5143 alt. my test flight.
I also used a back up alt. [perfectflite HiAlt 45] for this. Your doing same, good idea! First time using R-das . Second flight just went with R-das, graphs on same 2 last pgs.
Tim hit 11,400 something. Which you should approximate with the K-750, since yours should be very similar and it's the same case. [I think?]
The mach reading along with other data was bad. I mounted a GPS and live telemetry broadcast in this bird, but the R-das was faulty so the data was also. Good thing we used a Perfect flight as back up.
Even with the extra weight I would expect higher flight than the sims