I agree that all of the above thicknesses mention will not be full section if only filled with 1/4" of weld(even the .28" piece). If you did fill completely, you would still have a one sided weld which is a PJP unless the second side is addressed or backing was used.(IOW, not prequalified as a CJP, even with melt-thru)see 2.17.1
edited" whoops, I didn't read the first post very closely....you have a .28" thick piece joining to a .75" thick piece. Don't forget that you will need to transistion this joint see 2.7.1 and 2.16.1.1 plus Figure 2.2
edited again" wait......is this a base plate to a HSS(T-Joint)? or is this a butt joint?...the info I gave you is for a butt joint where two pieces are being joined of unequal thickness(non-tubular) You threw me a curve this morning when you stated a single V groove where both pieces are prepped...I'm not fully awake yet as you can see.....