171k

here is my way to score 171,000+.

all upgrades are interest.
you could score a bit more if you overlap towers towards the end. i was not up to the boring task, sorry ;-)

first number stands for level second number for number of tower.

1-simple tower

1+ - once upgraded

1++ twice upgraded

do not worry about an occasional leak.

1:1

2:1+

3:1+,1

4:2+ - sell one before level ends

5:1++

6:1++

7:1++,1

8:AIR - 1+ positioned middle bottom, 1 positioned to hit end area, sell the 1+ before end and the 1 at the end of level

9:1++,1+

10:1++,1+

11:5++ sell 2 before end of level

12:3++

13:3++

14:3++

15:3++

16:3++

17: Air - use tactics of level 8 with 3++ and 1+

18:5++

19:7++, sell 1 before end

20:6++

21:7++,1+

22:15++, goes through 3 times, sell 7 before end

23:8++

24:9++

25:10++

26:14++ sell as many as possible before end of turn

27: Air tactics - 9++ sell all of course

28:13++

29:17++

30:21++

31:24++

32:35++

33:35++ leaks twice.

34:50++

35: 65++

36-39 fill as much as you can (100++), buy lives if necessary.
sell as much as you can before the end of level 39 to get a bigger final bonus there.

level 1

level3

level 6

level8

level 11

level12
level13
level 17
level18
level19
level 20 level 21
level 22
level 23
level 24
level 25

level 26
level 27
level 28
level 29
level 30
level 32
level 34
level 35
level 36-39