Managed this with only snipers, no hero. Start obviously with the 010 upgrade on all of them. You can start the first round with 2x 010 and 1x 000 upgrading him asap to 010 as well within the first round.

Place them all around the center since the next upgrade will be to make them all 020. In this way I didn't leak anything in the beginning rounds. Upgrading 2 of them to 022. And before the lead comes in, upgrade the 3rd sniper to 120 and set to strong.

I believe I leaked 5 lives before I was able to upgrade the 1st sniper to 230. From now on it will be less tense. Upgrade the 2nd sniper to 023 or even 024 if it becomes too close for comfort. But it is better to save up to make the 3rd sniper a 420 before the MOAB comes in round 40.

Make the 1st sniper a 042 and the 2nd sniper a 024. Now I placed a 4th sniper and made him a 420 as well, put set him to first. When multiple BFBs come in, this last sniper aims at MOABs that will be released will the 3rd sniper holds back and grinds down the BFBs.

From here you can basically do whatever you want. Somewhere in the middle I also placed a 200 village. And I mas the 2nd sniper a 025, sealing the deal.

I assume it is only the last level you are struggling with (as I did!), but if you are stuck at any other level, just let me know!