Is it the Father or the Son being called "true God" in 1John 5:20?

It says:

" And we know that the Son of God has come, and has given us understanding so that we may know Him who is true; and we are in Him who is true, in His Son Jesus Christ. This is the true God and eternal life. " (1John 5:20, NASB)

Are there any reasonable, logical reasons to suggest that Christ is being called the true God as many Trinitarians claim?

The Reformation Study Bible comments on 1John 5:20:

"5:20 him who is true. Being in God who is true and being in His Son Jesus Christ go together inseparably. The grammar of this verse is difficult, but it is most reasonable to understand that “the true God and eternal life” is Jesus Christ. If the phrase refers back to the Father the verse becomes needlessly repetitive. Moreover, the phrase “eternal life” is applied to Christ in 1:2 as well."

The Deity of Christ is indisputable:

'RAPID FIRE VERSES: Jesus is Jehovah of the Old Testament' : http://bit.ly/2boCGaM
'Jesus Raised His Own Body From the Dead' : http://bit.ly/2c1A6do
'Jehovah the Son proven and established: 1Cor. 10:4, 9; Jude 1:5' : http://bit.ly/2dh0AFq
'Jesus definitely claiming to be Jehovah: John 8:58' : http://bit.ly/2cep5XE
'An Activity For Jehovah's Witnesses' : http://bit.ly/2bUmlLH
'Demonstrating the eternal Son from Scripture': http://bit.ly/1X6Ak4u