I have noticed that increasing the number of engineers and scientists working on same project at a time reduces the efficiency of their work.
Counting from the starting number of 6 Engineers, I got the following results:
1) Increasing the number of Engineers by 6 (6-> 12) reduces their efficiency by 6% (114 hours instead 107,5)
2) Increasing the number of Engineers by 12 (6-> 18) reduces their efficiency by 13% (81 hours instead 71,6)
3) Increasing the number of Engineers by 18 (6-> 24) reduces their efficiency by 20.9% (65 hours instead 53,7)
4) Increasing the number of Engineers by 22 (6-> 28 -maximum of available in the current version V17) reduces their efficiency by 28% (59 hours instead 46)
Counting from the starting number of 6 Scientists, I got the following results:
1) Increasing the number of Scientists by 6 (6-> 12) reduces their efficiency by 6.1% (78 hours instead 73,5)
2) Increasing the number of Scientists by 12 (6-> 18) reduces their efficiency by 14.28% (56 hours instead 49)
3) Increasing the number of Scientists by 18 (6-> 24) reduces their efficiency by 22.44% (45 hours instead 36,7)
4) Increasing the number of Scientists 22 (6-> 28 -maximum of available in the current version V17) reduces their efficiency by 27% (40 hours instead 31,5)
At the moment, in version 17, engineers can be divided into different projects if they are recruited on different bases (although it is not convenient).
Scientists cannot be divided at all, as the research window is common to all bases.
As a result, I find it necessary to allow the division of engineers and scientists between projects by the player, regardless of their base (as in the original x com), or to remove the reduction in their effectiveness.