How can I tighten gaps above the lip of recessed lighting?

maybe fill gaps with silicone from tube

You could try tightening up the metal spring or setting it up higher inside the can.

Russ,. I read your question, and I'm trying to visualize what your talking about. Those that are recessed, I believe are on a spring. I don't know how you can tighten them up. Take the bulb out, then lightly pull on the circle and let it go. See if that helps any. Aloha!

Always turn off the breaker before adjusting lamps. You need to find the post near the wires that attaches the lamp to the Box. You adjust that a couple turns clockwise to rise the lamp closer to the ceiling and you adjust counterclockwise to lower it. Many Electricians leave a slight gap about 1/72 to 1/48 of an inch for cleansing purposes.

If the gap is less than 1/32 of an inch this is Normal Professional Grade Technique.

If it is like an 1/8th inch or better then you do want to tighten it up, and should avoid that So-Called Electrician in the future, as they went blind or something, but never do you ever tighten that fixture all the way either, as

A. You will not be able to spring clean around the edges of it too easily if you do not leave room for the towel or scrubrag or sponge.

B. Walls expand and contract in the 4 seasons, so you do not want the ceiling fixture to crack or Mark the Drywall.

C. If it is too loose a client may injure by DIY and it becomes a Liability Risk.

Technicalities of Thermal Expanse and Loss-Lie Formula

For Journeymen as myself that actual Expand and contract rate essential to not crack plaster or drywall usually relies climate. To deduce this is the 'Loss-Lie' formula some journeymen are taught but very few ever really use.

The formula is bonkers:

1÷[(228-(8×Zone))-[(the difference Summer°F-Winter°F) × 7.055/7.13]]=Inches from the wall of the fixture.

So, the Agriculture Zone 3 differs 7 etc. Zone 8 works out as around 1/63 an inch...and most just use Zone 8 as the Average for everything and go with 1/48 to 1/64 of an inch everywhere by:

A. Asking a Client: Do you get Ice Cold Winters? Yes=1/48 and No=1/64.

B. Using a piece of the black wire as a Guage of how much space to leave.

C. Being accustomed, as doing it beyond 20 years.

It is called Loss-Lie not solely because it is often wrong in regions not Region 8, [otherwise Jar lids on unopened fruits or Jams placed in the fridge would be easier to take off, but we all know they never are, Tin shrinks more than glass, you gotta put it beneath hot water to get the darn lid loose] especially during summer installation of Cheap Garbage so many clients nowadays want, but Loss-Lie is to Remember the Goofy Fraction, (as you flip the Numbers 7.055=Loss and 7.13=Lie)

Anyways, usually this space falls between 1/48 and 1/64 of an inch not half an inch.