YankeeDog

During setup, don't worry about whether the HMG team is exactly in front of a window or not; the visuals aren't 100% WYSIWYG.  Rather, DEPLOY the HMG team into the building, and then check what areas they can target using the TARGET command.  Blue line = they can see and target the point where the cursor is.
 
Bear in mind that the TARGET line is intentionally somewhat conservative; units will sometimes be able to spot and shoot at enemy units beyond what the target line shows, especially in areas where you get the "Reverse Slope No Aim Point" alert.
 
If the MG's field of fire isn't to your liking, use the FACE command to change their deployment inside the building, and try again.  During setup, deploying HMGs in buildings is instantaneous so you can play around with FACE as much as you please. You'll sometimes find that fairly small changes in facing have a dramatic effect on LOF, so it's worth playing around for a while and even trying some FACE orders that are as much as 90 degrees off your planned vector of engagement.
 
Any way you slice it, though, there are usually limitations on the field of fire for an HMG in a building. This can be a good thing as a limited field of fire goes both ways -- it also limits the locations from which an enemy can directly fire back upon the HMG.  But if you want a really wide field of fire from a building, for HMG types that are allowed to fire "semi deployed" such as the MG42, you may actually want to leave the HMG only semi-deployed in the buildings so that the gunner can move quickly from window to window in order to engage new threats.

During setup, don't worry about whether the HMG team is exactly in front of a window or not; the visuals aren't 100% WYSIWYG.  Rather, DEPLOY the HMG team into the building, and then check what areas they can target using the TARGET command.  Blue line = they can see and target the point where the cursor is.
 
Bear in mind that the TARGET line is intentionally somewhat conservative; units will sometimes be able to spot and shoot at enemy units beyond what the target line shows, especially in areas where you get the "Reverse Slope No Aim Point" alert.
 
If the MG's field of fire isn't to your liking, use the FACE command to change their deployment inside the building, and try again.  During setup, deploying HMGs in buildings is instantaneous so you can play around with FACE as much as you please. You'll sometimes find that fairly small changes in facing have a dramatic effect on LOF, so it's worth playing around for a while and even trying some FACE orders that are as much as 90 degrees off your planned vector of engagement.
 
Any way you slice it, though, there are usually limitations on the field of fire for an HMG in a building. This can be a good thing as a limited field of fire goes both ways -- it also limits the locations from which an enemy can directly fire back upon the HMG.  But if you want a really wide field of fire from a building, for HMG types that are allowed to fire "semi deployed" such as the MG42, you may actually want to leave the HMG only semi-deployed in the buildings so that the gunner can move quickly from window to window in order to engage new threats.

Bear in mind that the attack profiles the Ju-87G is capable of while carrying the 37mm cannons are not particularly steep, so it can't achieve very "flat" hits against the top armor of an AFV except in special circumstances such as when the AFV is on a steep incline.
 
When carrying the 37mm gun pods, the Ju-87G is actually not a dive bomber -- to improve performance and reduce weight, the dive brakes were removed when the 37mm gun pods were carried, and the weight of the gun pods also dramatically reduced the ability of the aircraft to pull out of a steep dive quickly -- each gun pod weighed nearly 300kg and unlike a Stuka on dive bomb run, and the Ju-87G had to drag this weight all the way through the pullout rather than jettisoning it just before the nadir.
 
So the typical Ju-87G attack profile was actually a shallow dive.  Penetrations of e.g., the T-34 16mm deck armor might still be statistically possible, but at these aspects the side and/or rear plates (assuming a flank or rear approach to the target) would make up a much larger percentage of the target cross-section and therefore hits to these plates and/or the tracks and running gear would be much more common than top hits.
 
However, at least if the pilot pressed this type of attack to close range, 37mm APCR from a Flak 18 probably could penetrate T-34 side or rear armor -- bear in mind that much of the effectiveness of the T-34's side armor especially comes from slope, and plunging fire from a 30-45 degree angle will negate much of this slope.
 
It's still not a matchup that's particularly favorable for the shooter.  In addition to being *really* hard to hit a small target like a T-34 with gunfire when moving at 300+ kph (and only getting a few seconds on target, and therefore only a few shots per run), the behind armor effect of 37mm APCR is not good.  So a significant proporation of the penetrations achieved are going to cause only minor damage.