Your 2006 Sunline would be built like the 4, 2004 models I have/had. And what I am about to say, could hold true for many of the shower stalls if they have the lower flange lip I talk about below.
See these 2 pics. Sorry they are not the best to show my point but you can follow it. They were what I had on photo server to show this point.
At the bottom of the shower surround, there is an approx 1" tall formed flange shape of the wall outwards towards the center. It is part of the wall itself.
The shower basin has a 1" high lip on the 3 sides where there is no door. The wall flange on the shower surround goes over the top of the 1" high lip on the basin on the non door area 3 sides. The basin lip is then behind the wall flange.
The door area that has the Shub Shower retractable screen, has to be caulked to the shower basin or it will leak as there is a bottom rail for the shower screen. You also have to caulk at least about 1" down the sides of 2 walls that join to the door area or water will leak out onto the floor.
This now leave the 3 non door walls themselves with what to do with them. When my T2499 was brand new, it never had caulk on those 3 walls. Nor did our T310SR or the other 2 Sunlines we have.
Seeing that, I thought for sure the factory missed caulking those 3 wall areas. So I added caulk there in the T2499 and later the T310SR. In about 2 to 3 years time, the caulk would crack right down the center of the caulk. The crack came due to the flexing of the shower basin which has about a 5/8 to 3/4" thick piece of styrofoam under it. And the fact the basin is so thin it has to flex. Since the basin flexes, it has to move in relation to the walls or it would pull hard and damage the walls or the basin over time.
After I pulled one of my project Sunlines apart for repairs, I saw how the shower basin was made with the 1" high lip on it. In our T310SR we use the shower all the time. Every night I shower in it when we camp and so does the DW. The shower gets a lot of use.
After ripping out the caulk and replacing it 3 times in the T310SR, I came to the conclusion there is no caulk that can handle that amount to stretch and not crack over time. So for the last 5 to 6 years I have not caulked the 3 walls other then by the door area. The shower basin still flexes a lot, but there is no water leaks from the sides.
If the shower hose is spraying and falls down to the basin (slipped out of your hand etr) and starts spraying sideways at that joint, odds exist the water will blast up that basin lip. It happened once on me, but I was lucky enough none went up the lip for the brief time the hose was spraying down there.
Point being, you can caulk it if you want to. But you have to use a flexible caulk so it will move when the shower basin moves. And odds are high over time, it will crack. How long you will get depends on the caulk and the amount of use and age. When it does, you need to replace it or it can get funky in the crack as it cannot dry out all the time.
Using a high bonding adhesive caulk to bond the basin to the walls I would not recommend doing that. It could create long term issues with cracking the basin or the wall if the caulk seal is so good it will not move. Something has to give as the basin is going to flex under an adults weight on it.
I have had good results no longer caulking those 3 sides. And the gap that is there, is big enough to allow the gap to drain and dry out and not mold up. At least on the 2004 models I have. I have not experienced any mold in the gap since I started not caulking it. I did have mold when caulking it and the caulk cracked. You do have to caulk by the door area as I stated above if you have the Shub Shower screen or it will leak out. That retracting screen started in the 2004 models. It might be on some of the older ones, but not as a standard install. The shower curtain has been around a long time before the Shub Shower door came to be.
Hope this helps