We agree on having 500 AP banked by Jun, 125+60 when V front comes and the turn before 315.
The Pz ball is indeed powerful. As I said the x's are not for the carpet behind the main line. NO, NO, and again No. See previous posts. Something like this, the first withdrawal, (we're talking South here, wherever the Pz ball will be coming, ID'ed by recon) is far enough away such that the axis can't reach it for deliberate inf attacks, and would be at level 2 fort lvl. Even with 3 xx at level 2 fort the Pzs can break thru on their own, so you need the screen in front (x's) and in back, more x's and cav and rif xxx.
when the Axis inf is close enough to make deliberates, next turn, then back to next line. Four armies of a Hq with sappers and x's as attached units can be building new "temporary" stop lines as the Axis moves forward, you will get about 2 weeks of "stop" per line.
The 40 x's I mentioned, in 4 xxxx's, 8 per xxxx and two per hex, build quite nicely. That's 16 hexes of lvl 2 fort. 120 x's would give 48 hexes prebuilt and over 250, I like, over 100 pre built. "pre" as in before Jun. Not counting the Tk x's, so with them, even more, not in xxxx HQ.
Once summer gets going the x's can't build fast enough for lvl 2 so would need help from more powerful units, in selected areas.
Once your rifle xxx summer "love" is built, about 40 is what I like, then begin with the Tk xxx. The 500 Jun bonanza makes the first 25 rxxx.