Ahoy all, I have been a flooring contractor for 30+ years. From high end carpets to commercial sheet and heat welding to vinyl planks, cork, rubber, engineered wood and solids. Since my hip replacement a year and a half ago and by my surgeons recommendation, I quit doing carpet. I have decided to pick up the slack by adding wood refinishing to my offered services. Now, I have a firm grasp on paper sequences as well using my new belt sander, direct drive, edger and the other small fortune of tools and equipment I have purchased but lack experience. I also attended the Bona school in Denver and hav read A LOT but this never replaces the hands on experience you guys have from being on the job. My first question is as follows - I just installed a 3/4 white oak floor in a master bed room addition. I weaved a 3, 5 & 7 width plank into an existing hallway and throughout. where the new construction meets the old there was a small height difference and it carried though a couple tight areas (halls). I "edgered" them down and floated but I know in the end those slopes are still there. Q - would you recommend cross cutting the grain on my first cut (where sanding with the grain is not possible) with the belt sander to achieve a truly flat floor or use the direct drive with hard plates? My over/under is (typically) pretty drastic and I need to remove a 1/16 to 1/8 of an inch to make the wood to tile transition smooth anyway.
Your advice is appreciated... Be well

If you weaved into the older floor you must have matched the T&G so the weave in was successful.
The first thing I do when there is a big height difference between boards there is to use the edger with 40 or 50 grit to get close. You can take off the oversold at the ends of the weave in without going too far and harming the old planks.
When you get close with all the new boards you ought to be able to use the big machine to bring it all close to flat with diagonal sanding. Then straighten it off with the 50 grit to get as flat as you can.