Studio Desk Selection

[Keys1970]

I have several user ergonomic questions regarding which studio desk you use.

1. If the desk has the sliding keyboard tray, do you put the keyboard instrument on the tray, or do you put the computer keyboard on the tray?
2. If the instrument is on the tray, does the instrument bounce when you play? Does it matter if 61 or 88 keys?
3. If the instrument is on the tray and when using the instrument, do you frequently slide the instrument inward/outward in order to interact with computer software/hardware? Does one effectively play more than one uses a computer during the composition process? Depends I guess....
4. Some vendors don't have a sliding tray. They have what looks like to be a smaller desk containing the keyboard that sits under the main table/desk. This smaller desk may or may not slide, or may not slide very easily. Is the intent to frequently slide in/out when using the instrument keyboard with this design?

I find it hard to test out desks and research the above questions even though I live in a large city (Washington, DC). Thus, I post here.