I'm developing wallet system trading BTC, BCH and so on.
In BTC, I'm using
estimatesmartfee API to calculate by transaction size and
relayfee to guarantee minimum fee and it works well.
In BCH, though most of logic is same as BTC except
estimatefee is used in BCH.
However, as increasing transaction size by input UTXOs,
sendrawtransaction is often failed because of shortage of fee.
How should it implemented properly? What is it affected? I guess some reasons, If I need to use API to get proper fee rete from some sites, what is that site?