Keith,
I would be cautious when attempting to match Luftwaffe identifications of aircraft to Soviet types. The standard of identification in the Western Desert was not high, as repeatedly mentioned in the
Mediterranean Air War series. On the Eastern front, it was often even worse. As evidence, consider the numerous claims for LaGGs throughout 1944.
Ewald was probably identifying an inline engined Soviet fighter which did not look quite the same as others that he had seen. If the unusual feature was the cockpit configuration, as you propose, then the LaGG-3 was a much more likely opponent than the Yak-7 over the Crimea in early 1944. Over Romania in the middle of 1944, he could have seen old Yak-7Bs without a bulbous canopy, but that is highly unlikely. I wrote a short comment on the history of the Yak-7 here -
https://airlandbattle.wordpress.com/...and-a-comment/ .
The Yak-7 went out of production in 1944 and I understand that since the autumn of 1943 at the latest, all Yak-7b fighters were produced with a bulbous canopy. Note the confusing designation, the fighters with the new canopy were usually referred to as the Yak-7b with a small letter, while the Yak-7B with a capital letter was used to refer to the Yak-7 with BS heavy machine guns, in production from the middle of 1942.
I hope the above is of some assistance.
Kind regards,
Dan