Matt,
The thing with the Schmalturm is that it only worked with the 88mm if they flipped the recoil cylinders and made them concentric (which is why it has the funny shaped mantlet in the kit). To ease the loader's task behind the gun, I have also heard that a special, 'fat case' ammunition was being developed along with a vertical loading breech which together, functionally shortened the rammer-stroke length of the improved 88mm L71 ammo without giving up the 'magnum load' powder charge as muzzle velocity.
All of which is fine except that you have essentially redesigned the KWK43/L71 into a new gun for an _inferior turret_, both in terms of operating volume and protection. Yes, the Schmalturm is better than the original Panther design with that stupid mantlet setup and thin sides/corners which even lightweight AT weapons in the 37-50mm range are effective against.
But judge the internal volume likely to be available from the side views and compare them to the effective armor thicknesses of a nominal 'E-75' (VIb chassis)-
http://3.bp.blogspot.com/_KezhQ6waZT0/TFjf-gurKTI/AAAAAAAAXrI/VPxPMZp2QNA/s1600/pantff.jpghttp://www.nast-sonderfahrzeuge.de/fotosammlung/albums/userpics/10002/E75_-_TIGER_II_C_2seitenA.JPG..............Panther ST King Tiger
Turret Front: 120mm 185mm
Hull Front: 85mm 150mm
Bull Nose: 75mm 100mm
And then realize that late '43 specification changes to the schmalturm required an MG42 coax, a Sperwer night sight and room for command radios to also be included. In '44 this equipment list was expanded yet again to include stereoscopic range finders and provision for a stabilized periscope sight plus 60-70 88mm rounds.
All this in a tiny little turret which -is not- (at war end) optimized for the L71 like the KT is?!?! You can't even remove the loader because the 4rd 'clip' system and automatic rammer were for the 75mm KWK42 mod that was functionally obsolescent with the arrival of the IS-3.
OTOH, you have some similar problems with the KT turret in that the frontal area is not as well protected (as a function of mantlet overlap) as it could be and the forward turret roof slope offers a lot of exposure to plunging fires in what remains a 40mm thick vulnerable area common to all German armor. A vulnerability which would have to be increased (greater inclination angle = more relative target area = easer to-hit probabilities) even more to mate up with the turret front plate, if you extend the flat part of the roof forwards to allow for a level mount on the stereoscopic rangefinder heads.
Something which we know would have happened (was planned for) with the last run of VIb Tigers in what, July 1945? That kind of vulnerability cannot be permitted, particularly as the terrain again opened out in Germany and the threat started fielding tanks capable of engagements in the 2,000m ranges.
So... go for the bigger Tiger II turm, and save yourself the hassle of rebalancing the tank to a narrower turret ring. Also keep the traditional L71 (which was just about equal to the American 90mm and Russian 122mm) while retaining the option to go to the bigger 105mm Flak 38/39-
http://en.wikipedia.org/wiki/10.5_cm_FlaK_38Later.
The latter ordnance, while only 2ft longer overall than the 18ft KWK42, had almost 3ft longer breach section, courtesy of it's high elevation flak heritage and extended recoil cylinders and so -never- would have fit into ANY Panther turret .
Then simplify the subtle curves of the Tiger II's turret side armor-
http://www.achtungpanzer.com/images/tig2_kr.jpgInto _flat panels_-
sonderfahrzeuge.de/fotosammlung/albums/userpics/10002/DSC08773.JPG
In essence, the standard KT turret has one wide, 185mm turret front panel and two elongated, very vulnerable if highly oblique, 80mm side panels which are exposed in the 2-10 o'clock frontal sector to easy penetration with any degree of traverse as the turret warps inwards from about the mid point (under the commander's hatch).
If you instead 'bend' that 185mm turret front around into two angled cheek pieces, you end up with full depth turret protection across the entire frontal arc of perhaps 200-220mm swept equivalency. AND you can make the sloping section of the turret top (which is now both shorter in length and narrower in width) about 100-120mm thickness. Leaving the 80mm sides alone but 'retracting' their presented area much further back along the flank of the vehicle.
If the turret has a constant width, to the cheeks, it has greater internal volume at the same time it displays substantially narrower frontal area behind a larger mantlet (in essence, the flat front is little more than a slot for the main tube to slip thru) and this 'gun shield', instead of covering up a hole can essentially extend -into- the front armor, ala M1 Abrams. And thus can be anything up to 400mm equivalent thickness, depending on breach balance issues, strength of the hydraulics and the thickness of the elevation trunnions).
Point Blank: The Tiger II turret doesn't require any rebalancing or turret ring diameter changes on a Tiger II chassis. All that you have to do is modify the turret front to improve protection against 100mm class enemy AT fire and allow for the incorporation of bigger guns to compensate for threat caliber changes, later in the production run.