I have measured the turret too, and I found it too squat, I guess depends just where and how you measure. Its up to you. To me, it looks better w/the shim.
Here is a list of tweaks and corrections to the Tamiya M48A3. None of these "have" to be done, but they will make it more accurate.
1. Turret height should be increased by approx 1.5mm, which can be done by adding an 0.040 sheet styrene shim between the turret halves, which can then be sanded to the turret's shape.
2. Fill the motorization slots and holes on the model.
3. Three oval holes should be added to the drive sprockets at the 12, 4 and 8 o'clock positions to allow mud to clear from the sprocket. These are not present on the model, but were there in real life. Check reference pics for shape and location.
4. It's worth considering replacing the fender stays with PE items or homemade efforts of very thin sheet styrene.
5. Rebuild the stowage basket from thin wire; it really improves the model.
6. Add casting numbers to the turret roof, rear hull, and engine access doors.
7. Glue mantlet in place and fill gap with milliput to represent the canvas cover.
8. Replace the cover, fixing clips with plastic strip and add bolt heads.
9. If shown opened, shave off loader's hatch internal handle and latch mechanism, and replace with brass or plastic strip, rod and tube.
10. Turret water jerry cans have incorrect style filling cap.
11. You could replace the molded on tie downs on the turret with brass items.
12. Use copper wire to add 3 lifting lugs to the commander's cupola, at the 12, 4, and 8 o'clock positions.
13. Shave off and replace the hull stowage bin handles with plastic/brass strip.
14. Fill up the main turret site periscope, as well as the driver's periscopes.
15. Add cast texture to the turret and hull.
16. Replace the awfully incorrect kit tracks with aftermarket ones. The AFV set is great, just make sure you get the correct one, they make two sets that they say can be used on the M48 and M60 tanks. One of them has octagonal shaped pads; the other has chevron shaped pads. The latter (chevron block) are the correct ones for a Vietnam era tank.
17. Suspension height correction. The Tamiya kit was based on a vehicle that did not have the engine installed, as such, it was lighter and rode high on its suspension. The kit is about 3mm too high. To fix it, shorten the suspension arm dampers by about 2.5mm by removing the thin rod on the shock part. This will allow the road arms to sit lower. You may also have to remove a couple track blocks on each side to take the slack out of the track.
18. Not so much a tweak, as it is a hint, do not add the barrel for the .50 cal to the commander's cupola. Do the other option the kit gives you and position the .50 cal outside and on top of the cupola as most tanks did this, because they felt the .50 cal took up too much space inside the cupola, restricting movement and vision for the commander. Fill the hole for the original position.
Good luck.
