The answer, of course, is VERY hard. The initial production Tiger I differs on nearly every important surface of the vehicle. Stowage is in different places, the front fenders are different, the turret stowage boxes are field modifications from a Panzer III, and so on. Starting with the rear hull, there is less stowage and the exhaust system is different from the early production Tiger I. Unfortunately it was easier to remove all of the detail and replace it than it was to simply modify the existing details. The photo below shows the rear hull with replacement fittings. The miniature was slightly concave, so there is extra green putty building up a smooth rear hull. The photo below that shows the prototype exhaust pipe (at left) along with the prototype front fender (which had a distinctive diamond tread surface). The prototype exhaust was built from aluminum rod, styrene sheet and tubing. A micro-punch was used to create the rivet detail. The fender is simply some mesh glued over the top of a styrene sheet cut and bent to the right size and angle. I've cast up several copies of both of these parts as each tank requires two exhausts and two fenders.
Additional modifications to the hull are fairly extensive as much of the stowage is moved or absent. The small side tow cable is not found on the initial production Tiger I, nor is the front shovel or the S-mine launchers. These were all therefore removed. The bolt cutters are also in a different position. Perhaps the most significant change was the location of the primary tow cables. Rather than the connecting eyes being stowed forward, they are stowed aft on the initial Tiger I, which meant the entire tow cable had to be replaced. I used styrene sheet, copper wire, and resin copies of the eyes from the original miniature as replacements. The initial Tiger I also had only five, not six, gun cleaning rods. These were replicated with stretched sprue.
Now that the primary surgery is done, I need to finish neatening up the miniature for assembly and painting. The fenders and exhausts will be attached prior to painting, but I generally wait until after painting to attach the tracks. The Tigers of the 502nd are all gray with substantial whitewash. I'll also need to make up custom decals as the markings are completely unique to this unit, but it will give me a chance to try out my new dry transfer maker!
Ultimately this will all go into an Eastern Front army using the Schwere Panzerkompany 1942 list. I know it's not the most competitive list out there, but it will be RIGHT for these guys. I'm also including some winter mid-war grenaders in the mix, so it should look great on the table, even if I die heinously! I'll post more "in progress" photos as this one works its way through the queue.