Zonos Duty and Tax

I added this app so that my international customers weren't blindsided by taxes and duties upon receiving their packages, but I've had nothing but trouble with it. The support people who work for this company are awesome (hence the two stars instead of one), but unfortunately the app itself is terribly inaccurate. I worked with several of my international customers to ask them what their taxes were and they were absolutely never even close to what Zonos estimated for Landed Costs. They were always way higher than my customers had to pay. Additionally, simple things like adding UPS shipping was difficult because, again, the rates weren't even close to what I'd pay to ship via Shopify Shipping. I'm worried that the overestimations are scaring people away during the checkout process. I've just changed all of my shipping fees to say "You may be expected to pay taxes/duties upon receipt of your item." Problem solved and now I get to keep my $20/month plus whatever percent they were taking per international order.